There are two ways to look at it. Sure, if they go far in the tourney, Marquette is more likley to pay up to keep him around.
But, think about it like this. The more success he has this tournament, the more expectations he will have. He will be expected to be sweet 16 or better every year, at Marquette, in the toughest conference out there.
If he leaves, he leaves the program in great shape, and has a legacy of winning there. That's the best way to leave a program. If he really wants to get closer to home, there couldn't be a better time than now.