Since the NFL name is the truly valuable product I would assume that the NLF holds all the cards. I don't think the NFL could start a competing game on the Wii U but they probably have enough sway to force EA to make a Wii U version if they want it.
In the end the deal expires and the NFL says "**** you, you neglected a platform for petty personal reasons, no more NFL licence for you" and EA is **** out of luck. No one would give a flying **** if some other company had the exclusive NFL licence and the game didn't have "Madden" in the title. If the NFL wants it on the Wii U, it's going on the Wii U and that's that. And EA only has their Madden cash cow if the NFL wants them to.