An interesting factlet is that Xenoforo can convert vBulletin 4 forums but not vBulletin 5. (last I checked)While I may not comprehend the technical issues involved, my instincts tell me that option 3 is the way to go as long as the history can be preserved and transferred over.
Now I feel smug about having donated a little All I need now is a forum-fitting car...We are not going to VB5 as there is no compelling reason to do so, we'd lose compatibility to some of our VB4 add-ons and custom work would have to be re-done again at $$$$. For now I think we are sticking with VB4 and continuing to enhance what we have, for example making mobile apps for Android and iPhone, etc.
Dud you are correct this is one of the last large forums NOT to sell out to the firms that buy forums. I've been approached to sell and much like Shark Tank I've told them that I am willing to take on an investor/partner but I don't have any interest in selling outright. They don't seem to understand that model, they just want to cookie-cutter everything.