[spkguitar]

My personal opinion is that you should wait until the project is done, especially if you already have multiple hours of work invested.

There are a LOT of differences between 8 and 12 (different file formats, etc), especially when it comes to plugins. All of your 3rd party plugins (and even some Avid/Digidesign ones) will need to be updated to the new format, and some (even some Avid/Digidesign ones) are not available as AAX.

Here's a recommendation for you: clone your system drive to an external, boot from it and do the updates. That way you have the original drive and system available to boot into, and the new system on a bootable drive that you can experiment with, and all it takes is a restart.

If you decide to work on any of the project files on the new system, copy them first so you have both old and new available as well.