Let me ask you this, do you think we will live to see a fighter who can hold a Boxing belt and a MMA belt at the same time? That would be awesome if some guy will achieve that.
That's a good question. The styles are so different, that on the face of it, I would say probably not. Boxers are specialists at what they do, and MMA doesn't require the same amount of specialization, since they can simply use another tactic (ie; clinch or submissions) entirely if they get outclassed in striking.
But........it's not impossible, and as kids are starting from scratch in MMA, as opposed to coming into it from other disciplines, they could conceivably have the time and energy to develop champion-level skills in both.