According to Apple's FAQ's, Final Cut Pro 7 (and therefore FCS3) should run with Lion:
"But if you’re already working with Final Cut Pro 7, you can continue to do so after installing Final Cut Pro X, and Final Cut Pro 7 will work with Mac OS X Lion."
I'm using it with OSX Lion right now on a Developers GoldMaster. The good thing is that Lion is not that much different under the hood to SnowL. It's got some great new features, my fav's being Versions and Resume. But these don't affect the day to day running adversely. Apps will have to be rewritten to utilise some of the features (so FCS3 won't get a look-in then).
So far I've not had issues with any of my main software including the Adobe CS5.5 suite, FCS3, PFMatchit, Parallels, Maya, Nuke, all working as they should - some much better!
Apple have just asked developers to start submitting their Lion apps so it will probably see a release very shortly. Next tuesday if they follow tradition. If you have 3rd party hardware for FCS or Logic you might want to wait until drivers have been released though. My NVidias work fine but if you use ATTO, AJA or Blackmagic cards you are best checking with these developers before upgrading to Lion.
All the best