You're wrong here in thinking that vendors need to wait until Ivy Bridge. They have the option of doing exactly what Apple is doing today. Some may very well do just that, but more likely they're going to wait until Ivy Bridge. Thus it's not an exclusive deal, but rather may remain an Apple advantage until Ive Bridge comes out.
Actually, the 17" MBPs have 3 USB ports. Why? Why not just give one and make users carry a hub around? You may think for your use that 1 USB port with a hub would hit a bandwidth wall, but most users see it as a hassle to carry a USB hub just to connect an iPhone and external drive at the same time.
The reason why Thunderbolt will replace USB ports is because it can. A DisplayPort more than fulfills the need for a DisplayPort, but yet Apple did away with it because there's no point in having one when there's Thunderbolt.
This is one of the key reasons for the development of Thunderbolt. The idea is that you have one port to rule them all. You take your devices and you plug them in without having to think "this one goes into this port, that one goes into that port". You have ports, you plug your devices into any of the available ports. They're all the same.
"This happened before". Serial and ADB ports were fine for keyboards and mice. For that matter, so was USB 1.1, but now it's just USB 2.0. This is because it's easier for the end user and cheaper and easier for the PC maker as well as the device makers.
Again, this is the whole reason why Apple requested Thunderbolt as a something everything else could roll into. There's no need to consider "Mice only need the speed of USB 1.1, so put a USB 1.1 port on there, and then put USB 2.0 for devices that need that speed, and FireWire 800 for devices that need that speed, and DisplayPort for devices that need that, and then Thunderbolt for only the stuff that needs that".
When Ivy Bridge is released, removing the legacy ports and having multiple Thunderbolt ports becomes cheaper, easier, and requires less space.
Yes, this is one fantastic use of Thunderbolt. There will be hubs and there will be docks, but not everyone has a desk station that they connect there notebooks to, and many people need connectivity to devices on the road. Thus it makes sense to have multiple Thunderbolt ports and the ability to plug all devices in.
Why did Apple include an SD card reader...you can just connect an external one. Why include an optical drive...you can just connect an external one...the list goes on. The issue is more than bandwidth, it's about convenience.
How can a vendor do what Apple is doing today? Do they have access to Thunderbolt controller chips? Anyway, it's a small matter really in the grand scheme of things.
I take your point that having one port type is an advantage, but having three Thunderbolt ports at the expense of USB ports would be insane in 2011, and probably 2012 and 2013 as well. People already own USB devices, many of them. Thunderbolt won't be ready to replace USB for a good while. Also, will licensing be as cheap for a new tech like Thunderbolt as it is for USB? I don't know, just musing.
USB unified several standards that were all existing simultaneously. PS/2 was being used for this, Serial for that etc. It was messy and they were old, not particularly practical (in a physical, disconnecting, reconnecting sense) ports. USB could just be slid in, done. People liked that.
Also, serial was far slower than USB is today and USB really took off when 2.0 came along. There was a need for more speed for all manner of uses. There isn't any now. Only storage really needs it. Your points are good, I just think that people won't see the same problems with USB as they did with all those old 1980/90s things. They'll think 'why do I need another type of connector? USB was fine.'
I don't carry a hub around with me. I find only having 2 ports a pain. I bought a Bluetooth mouse just to free one up. I'm not for a moment suggesting we all have one port and connect everything via a hub. I'm saying that USB ports are far more useful to every single user right now and will be for some time to come. I think Thunderbolt's primary use for a while will be to conduct other devices into the computer via a hub.
When the 1,080,000p webcam comes out, we might need a Thunderbolt port adding... I believe Thunderbolt ports could replace USB like you say, but it won't happen for a very long time. Until then, adding more Thunderbolt ports and losing USB ports would mean carrying adapters around for existing devices. That's as bad as needing a hub.