It's a bit late don't you think Nintendo knows what sells there not gonna change and do something revolutionary now or ever they know the minimum to get the sale and they will milk Mario for years enjoy.
I love NSMB. That said, I wouldn't be against them mixing up the formula. Letting Peach be playable, letting there be a different main bad guy other than Bowser (perhaps with Bowser appearing halfway through to harass you, etc).
I love Bowser, don't get me wrong, but I appreciate a little variety, too.
I am Lord Bowser, King of the Koopas! Bwahaha.. Playing Bowser on Mario Kart, and Noxus on Metroid Prime. I am not a cookie cutter!
NSMB is getting stale. They need to do something really interesting to keep it fresh for people, but they won't because it still sells regardless of how similar the new game is to the last one. Luigi U was a good start, but that game's mechanics probably should have been the way that they went in instead of NSMB U.