Seems like two different questions to me - future of forum software vs. future of vBulletin specifically.
I think forums will always satisfy a need that cannot be replaced by social media. People love to interact with like-minded communities about shared niche interests. In fact, with successful forums, I see more loyalty & thought put into posts than on huge sites like Facebook.
As for vBulletin, I still think it's one of the best forum softwares out there. I also liked IPB and phpBB, although my most successful forum has been on vB. Haven't tried xenForo, mainly because it feels "lonely" to me (I can't really explain why).
Having used vB 3, 4, and 5, I believe that 4 is the best version. More specifics in your question might help. I'm wondering what made 4 less cool than 3? What is the "actual" vBulletin?
It's strange that you say 5 is not looking any different than 4. They feel drastically different to me, in a bad way. You certainly wouldn't be the first to be frustrated with vB5, but I would highly recommend giving 4 a shot. Our members have been extremely happy with it, and have quickly voted against using various other softwares (or going back to 3)