XCode may be coming to the iPhone and iPad very soon
Apple could be in the process of developing a version of XCode to run on iPhones and iPads in iOS 14 and iPadOS 14, a leaker claims, a rumor that could lead to mobile apps being developed on the devices they will be ultimately used on in the future.

The iPhone and iPad are capable of a considerable number of tasks, with some people using the mobile devices as fully-fledged replacements for traditional computers and notebooks, like the MacBook Pro. One area that Apple hasn't covered so far is on-device development, which may change with the introduction of iOS 14 and iPadOS 14.
According to leaker Jon Prosser in a tweet posted on Monday, XCode is "present on iOS/iPad OS 14." Claiming he mentioned its existence during a live stream the week before, Prosser goes on to suggest the implications are "huge," as its inclusion "opens the door for 'Pro' applications to come to iPad."
As an example of what he alludes to, Prosser comments "I'm not gonna say that Final Cut is coming to iPad," referring to Final Cut Pro X.
Prosser's comment was elaborated upon by a reply from iOS developer Steve Moser, who points out "the hidden Xcode Preview app is present in iOS 13," though it is used as a companion app for the Mac-based version to show layout previews on a device's screen. However, in response to another message suggesting it could be the Preview app, Prosser hints it's not that by suggesting "I know more than I've shown."
So far, Apple has not allowed iPhone and iPad users to develop apps directly on the devices in an official capacity. The nearest it has allowed is Swift Playgrounds, an iPad app that teaches Swift development and experimentation, but stops short of app development itself.
It's not clear how a full version of XCode for iOS and iPadOS leads to "Pro" applications on iPad. Given development for the platforms via a Mac already exists, it would be more prudent to consider the addition as making it easier for people to produce apps in the first place.
Currently a Mac or MacBook is required to develop an iOS or iPadOS app, though it is possible to test apps and visualize app layouts during development. By making it possible to develop on an iPhone or iPad, this can enable more people to get started creating apps as they don't need to acquire a Mac beforehand, reducing the barrier to entry for development.
Apple's plans for iOS 14 and iPadOS 14 won't be fully known until WWDC 2020, with Apple typically using the developer conference to unveil changes in its major operating systems.

The iPhone and iPad are capable of a considerable number of tasks, with some people using the mobile devices as fully-fledged replacements for traditional computers and notebooks, like the MacBook Pro. One area that Apple hasn't covered so far is on-device development, which may change with the introduction of iOS 14 and iPadOS 14.
According to leaker Jon Prosser in a tweet posted on Monday, XCode is "present on iOS/iPad OS 14." Claiming he mentioned its existence during a live stream the week before, Prosser goes on to suggest the implications are "huge," as its inclusion "opens the door for 'Pro' applications to come to iPad."
I'm not gonna say that Final Cut is coming to iPad...
But XCode is present on iOS / iPad OS 14.
The implications there are HUGE.
Opens the door for "Pro" applications to come to iPad.
I mentioned this last week on a live stream, but figured it was worth the tweet-- Jon Prosser (@jon_prosser)
As an example of what he alludes to, Prosser comments "I'm not gonna say that Final Cut is coming to iPad," referring to Final Cut Pro X.
Prosser's comment was elaborated upon by a reply from iOS developer Steve Moser, who points out "the hidden Xcode Preview app is present in iOS 13," though it is used as a companion app for the Mac-based version to show layout previews on a device's screen. However, in response to another message suggesting it could be the Preview app, Prosser hints it's not that by suggesting "I know more than I've shown."
So far, Apple has not allowed iPhone and iPad users to develop apps directly on the devices in an official capacity. The nearest it has allowed is Swift Playgrounds, an iPad app that teaches Swift development and experimentation, but stops short of app development itself.
It's not clear how a full version of XCode for iOS and iPadOS leads to "Pro" applications on iPad. Given development for the platforms via a Mac already exists, it would be more prudent to consider the addition as making it easier for people to produce apps in the first place.
Currently a Mac or MacBook is required to develop an iOS or iPadOS app, though it is possible to test apps and visualize app layouts during development. By making it possible to develop on an iPhone or iPad, this can enable more people to get started creating apps as they don't need to acquire a Mac beforehand, reducing the barrier to entry for development.
Apple's plans for iOS 14 and iPadOS 14 won't be fully known until WWDC 2020, with Apple typically using the developer conference to unveil changes in its major operating systems.
Comments
iPadOS makes some sense now that it's a operate OS that includes increasingly improves mouse/trackpad and keyboard support, but as you note, it's not a great experience on a small display and I don't see how it would get a lot of use on the iPad without some major revisions since you still need to design everything with a finger as the primary input choice.
There are still things to do on the hardware front, such as 8, 16, and 32 GB RAM options, and external display support.
I think what this really means is that it will now be possible to compile code on iDevices.
Note that compiling code is not just something that software developers do when they are writing apps.
Compiling code on the fly in response to input makes for better, more flexible apps (especially think AI/ML).
But it also makes for a much greater security risk.
So the issues in play here are security vs features/flexibility.
Bottom line --- this has almost nothing to do with UI, it has almost nothing to do with people doing software development on an iPhone.
I think it would meet the definition of hazing to assign Apple staff to rewrite XCode IDE (including Interface Builder!) to work on a phone (small screen, no keyboard, no mouse, etc.).
The same people that use this, probably:
https://apps.apple.com/us/app/pythonista-3/id1085978097
I started programming in BASIC almost 40 years ago on pocket computers with very limited screen real estate and rudimentary toolset (to say the least). Between then and now and through many high level languages and platforms my constant desire has always been to obtain more and more screen real estate through every means possible, including larger individual screens, multiple screens, more larger screens, using iPads as auxiliary screens, eye numbing tiny font settings, etc. A lot of this constant need for even more screen real estate was driven by a constant increase in the number of auxiliary IDE windows and information density that became essential for both development (writing and managing code), monitoring/tracing, and debugging. As the number of auxiliary windows and information density increased the space left over for code editing windows got smaller and smaller, only increasing the need for even more screen real estate. Not to be left behind in the feature bloat department, code editing windows got increasingly more complex and feature rich with multiple tabs, split panes within tabs, a ton of contextual information overlaid on top of the text, like syntax coloring and highlighting, auto completion hints, error indications, deeper context menus, etc., putting even more demand of more screen space.
Now we're talking stuffing all, or some subset of that, into an iPhone? I'll be the optimist and say, "bring it on." If Apple can pull this off and the net result is something that is intuitive, productive, and useful to a broader population of professional and enthusiast developers who have hit the wall on trying to accommodate the constantly increasing demands of modern IDEs like XCode, Visual Studio, and Eclipse - I'll be more than impressed.
Anything that can be done to make software development more accessible to a broader group of people will be a benefit for society as a whole. Having the ability to navigate the complexity of a modern IDE and unforgiving languages like C++ and Objective-C (and to a lesser degree Swift, C#, and Java) is certainly commendable in a Spartan punching-bark-off-of-trees sort of way, but it's also a huge exercise in rewarding claptrap and complexity and sustaining misguided priorities. At some point, which probably occurred about 20 years ago or more, developers started to serve the tools rather than the tools serving the developers. It's time to flip the script and hopefully Apple can show us the way.
The only thing I don't get about Xcode on the iPad is, about a quarter of the time I spend in development is in Terminal. I don't know how you do useful dev work on the iPad without a terminal and root access.
Yes, this by definition is a "what should have been". Not sure how rationality applies here as I'm specifically disagreeing with Apple's chosen development path for the iPad when I say they should have done something different in the past. That's entirely rationale, and something everyone of us does. There's nothing that can be done about it now other than complaining, but entirely rationale to say Apple should have done something different, just like it is entirely rationale to say Apple messed up the Mac Pro for 5 years, and should have done something different, something faster to address the issues with 2013 Mac Pro.