I think you'll see a gradual replacement of boxing as the premier "fighting sport" with ultimate or hybrid fighting over the next few years. Boxing is so convoluted and confused, with no clear ruling body and no clear champion, that people get tired of watching watered down club matches disguised as heavyweight bouts.
UFC is getting more refined every year, and is beginning to have that "complete sport" feel to it, while still retaining the "anything can happen" factor. Plus, it appeals to the fans who are in it for the blood and guts. They went through a period that could have killed them when everone was doing chokeholds, but recent rule changes seem to have addressed that.
Aside from that, hybrid or UFC style matches are seen as truly tough man contests, with more availability and accessability to the common guy than boxing has. And aside from a few offshoots, the majority of world-class shootfight athletes wind up under the UFC sanction, which lessens the confusion of who's governing what bout.
I'd give it about 5-6 more years before UFC overtakes boxing as a sport...