My advice to anyone hesitating to drop $140 plus the commitment of choosing to install Xenforo is to go ahead and do it.
Shawn Hogan of
http://forums.digitalpoint.com/ is migrating his vBulletin 4 forum to Xenforo. Shawn has invested a huge amount of time coding the extra functionality he needs to get Digital Point working on Xenforo. He wouldn't do that without good reason. And that reason, as he pointed out to me, is that whatever happens to the lawsuit, Xenforo remains the best core forum product.
I agree and I think that whatever happens to Xenforo, there will be a community of good coders creating addons.
For me at least, there is no better alternative product at the moment.
And AVForums is at vBulletin 3.8 and I haven't installed any upgrade (and won't) since Kier left, so we're effectively unsupported. So for me I lose nothing in that regard if I upgrade and the lawsuit is a disaster.
And I don't think the lawsuit will be a disaster. I think XF will win.
So my best advice to anyone considering installing Xenforo is to go ahead and do it. That's the best option I see right now.