New support document spells out compatibility of Apple's Pro apps with High Sierra
A support document published in advance of Apple's impending release of High Sierra details what versions of Apple's Pro Apps will work fine in High Sierra -- and what has been left behind.

In the document published on August 18, and an email sent on Tuesday and Wednesday to prior registered users, Apple notes that some versions of Apple Pro Apps aren't compatible with High Sierra and won't launch.
The oldest versions compatible with High Sierra are all the most recent versions, including Final Cut Pro X 10.3.4, Motion 5.3.2, Compressor 4.3.2, Logic Pro X 10.3.1, and MainStage 3.3.
Applications left behind by the update include Final Cut Studio, and Logic Studio. Both Logic Studio and Final Cut Studio are 32-bit apps, and were last updated in 2010.

The High Sierra update to macOS is intended as a refinement of Sierra, much like Snow Leopard was to Leopard, and Mountain Lion was to Lion. Improvements shown at the WWDC keynote include Safari refinements, Photos speed enhancements, the inclusion of Apple's APFS, H.265 support, and Metal 2. Any computer capable of running Sierra will be able to upgrade to High Sierra.

In the document published on August 18, and an email sent on Tuesday and Wednesday to prior registered users, Apple notes that some versions of Apple Pro Apps aren't compatible with High Sierra and won't launch.
The oldest versions compatible with High Sierra are all the most recent versions, including Final Cut Pro X 10.3.4, Motion 5.3.2, Compressor 4.3.2, Logic Pro X 10.3.1, and MainStage 3.3.
Applications left behind by the update include Final Cut Studio, and Logic Studio. Both Logic Studio and Final Cut Studio are 32-bit apps, and were last updated in 2010.

The High Sierra update to macOS is intended as a refinement of Sierra, much like Snow Leopard was to Leopard, and Mountain Lion was to Lion. Improvements shown at the WWDC keynote include Safari refinements, Photos speed enhancements, the inclusion of Apple's APFS, H.265 support, and Metal 2. Any computer capable of running Sierra will be able to upgrade to High Sierra.
Comments
I am not sure if HFS and APFS can coexist on the same drive or not, but I have my bases covered either way.
https://forums.appleinsider.com/discussion/comment/2971420/#Comment_2971418
http://appleinsider.com/articles/17/06/07/high-sierra-runs-on-all-sierra-capable-hardware-starts-process-to-kill-32-bit-apps
The following command will list 32-bit binaries in the command-line:
find /Applications/ -type f -perm +111 -exec file {} \; | grep "executable\ i386"
Sometimes applications are built as 64-bit but the frameworks/libraries/bundles that they use aren't. If they are going to stop the OS running 32-bit binaries, that's going to break a bunch of apps. XCode won't be able to run simulators of old iOS versions.
Quicktime Pro will go too and neither Quicktime X nor FCP X support all of its features like passthrough encoding.
I can understand removing the ability to produce 32-bit apps but why break all the runtimes? When they transitioned to Intel they put Rosetta in to run PPC software and it was needed for a couple of years. In the case of older 32-bit apps, some will never be updated again because they are just simple, useful utilities that do what they need to do and don't need to be updated. Surely they can have some compatibility software that just lets 32-bit apps still run without needing to partition and maintain a whole operating system.
I'm switching back and forth without any issues (making sure not to let beta 10.13 update my Photos in the cloud). You can just experiment with an external clone of your regular internal and update that to 10.13. That way you can enjoy the fun without risk.