I think it's also an important thing to note that Playtonic expressed a lot of interest in working with Nintendo. While they also said that they want to get it to as many people as possible, they seemed so excited about working with their old partner again. Their interest in Amiibos also kindof leans toward Nintendo exclusivity, as I don't know of any multi-platform games on Nintendo systems that have Amiibo support (although if there are, please correct me).
Not to mention if they're making it for a specific console, they will make it for the engine associated with it to the best of their abilities. Things won't have to be changed quite so much if they're not jumping around all the time.
In other threads about console exclusivity, people outright say that "Nintendo will be where I buy it because it feels right". WILL it sell on the XBox or Playstation? Are there that many XBox/PS4 exclusive gamers with interest in this game? I don't know. It's still so early, I'm just thinking out loud. Spreading themselves thin could be a problem, too.
Despite this, I do agree with you guys right now in the current state of what we know about the game. Get it everywhere, right on. I'm just thinking.