PartSkeptic
Illuminator
Honestly, if someone won the MDC, I would be very very curious about the situation, and I certainly would think it deserved further attention, but it would be far from conclusively demonstrated. I'm able to be convinced, but it's going to take more than one reputable test to do so. I suspect that you (and the bulk of the skeptical JREFers) would likely react in the much same way.
I'd be far more inclined to think that it was a particularly clever cheater or a test that was flawed in some way rather than someone who can actually read minds. Heck, if I were a betting man, I'd put money on Randi intentionally throwing the contest over actual paranormal stuff. Neither is likely, but there are a whole lot of people who have done a whole lot of crazy, unexpected stuff, and there are still zero people who have shown themselves to be psychic.
I agree. I think if someone won, and refused to repeat the experiment, JREF would have a new challenge: $1 million to the person showing how the cheat/trick was done. Despite the odds, people would say that in effect there was only one demonstration, and a refusal to repeat it for science to study would be seen as "trickery".