I don't see how a Mario Rabbids RPG out beats a 3d Mario. Mario Kart for sure, but as I said, if they have two games, a 3D Mario and a Zelda, the 3D Mario will be the one. More marketable and sells more.
just thinking about strategy.
they want early adopters to create a big buzz about the system, and their sights aren't set on record sales (2m worldwide). zelda does that better than mario - especially an open world zelda that's been getting huge buzz already thanks (or in spite of?) three years of promotion.
with mario rabbids rpg, i don't think there's any better time than to release it at launch. that's the sort of thing that's a weird novelty and needs the launch window to sell. people might pick it up as though it was a mario platformer instead of the one that's coming later. they sort of did the same thing with super paper mario and super mario galaxy in 2007.
and i think it makes sense to keep that ball rolling with mario kart a month or two afterwards. regardless, within six months it sounds like there will be three mario games. something in the summer to keep momentum up is probably better from their standpoint than to shove all of the original games into launch and have only wii u up-ports through the rest of 2017.