If the UFC wanted to buy out Bellator, I'm sure they could have done it long age. But what would be the point? Aren't they involved with ongoing anti-trust litigation. That would be the last thing they'd want to do.
Bellator is no threat at all to the UFC. It nothing more than an annoying bug to them at contract negotiation times. In fact, it's very existence is a benefit to the UFC to show it's not, in fact, operating as a de facto monopoly. But that mentioning of Bellator on the last PPV was dictated by the UFC marketing people, and I wonder: why now?
I'm not sure what the value of the brand would even be at this point. It's not like they've ever managed to develop much of a fan base after all these years. I think there core fan base exists in some of the people who post here.
Anyways, I hope they can get it together and start putting out some good cards.