Personally I believe the UFC will continue to grow to be the leader in MMA fighting, perhaps so large it will dwarf the others. Basically this has nothing to do with Dana White or Zuffa being geniuses, but they happened to fall ass backwards into a huge money making opportunity, reality television. Not only did it get the sport out to the masses, but it gave the UFC credibility in that people now have a glimpse of what it takes to be a professional MMA fighter.
In terms of what will happen in the UFC with the titles and whatnot, here's what I believe by division in the next few years:
Lightweight - If BJ Penn can successfully cut the weight, he will dominate this division for the next little while, if not the championship will change hands frequently.
Welterweight - GSP, not much to say here, as long as it dosen't go to his head and he becomes a lazy rock star, GSP will continue to dominate.
Middleweight - Who knows, the most open of all the divisions, being from Edmonton, Alberta, Canada, I suggest Jason MacDonald will be the force to be reckoned with after disposing of Rich Franklin and Anderson Silva in stunning fashion, lol. I really don't know with this division.
Light Heavyweight - Honestly I think Rampage and Chuck will be the next big rivalry. Chuck beats Rampage in mid-2007, then Rampage stuns everyone by beating Chuck late 2007. Tito becomes non-existent this year unfortunately, or at best beats some of the TUF guys non-convincingly. Does he care, probably not, he's a millionaire and bangs Jenna Jameson, do I blame him for not being motivated anymore, nope. One thing that could make the division REALLY exciting, IMO, is if Brandon Vera could cut the weight and enter the division, that would be cool, I think he could be dominate for a while.
Heavyweight - Tough one here, lol. Mirko is too good for anyone in the UFC, they try to spin Tim Sylvia a rematch/rivalry after Mirko beats him mid-2007. But Sylvia gets exposed, they Mirko continues to kick butt until someone else comes into the division to rival him.