It's safe and your old puppets should still work by default, but if you want to do anything serious with them in the future, I'd recommend updating their triggers using the conversion process outlined in https://youtu.be/1iS0gUoe1i8
Bottom line: if you're in the middle of a big project and already have recordings, I would stick with the old version until you finish the project, then update.
Thanks for such a quick reply. I assumed it was safe but this is hundreds of hours of work. The project is mainly over (gonna be releasing on TBS Digital at the end of November) but there's still a chance for revisions or other work.
I guess the safe play is to wait until it's completely over but dammit, I've been begging for waveforms for two years!
If I update and it somehow wipes the scenes and puppets, can I revert to the previous version and load a backup of the project file? That works, right? (sorry for bothering you about such basics)
Oh wow! If it's hundreds of hours of work I would definitely not update yet. I love waveforms too but I wouldn't risk it!
Yes, if you saved backups of everything and had the old version, that should still work. But as soon as a project (chproj file and those media/data folders) get brought into the new version, it gets converted and isn't backwards compatible, so definitely make sure the backups are safe with all the necessary reference files.