Wow, what a crazy announcement! Personally, I couldn't be less excited for it but whatever.
I do think that that "more kids know Mario than Mickey Mouse" is kinda taken out of context here though.
I would guess Universal tests out the American market for a while, selling merch and having some promotional tie-ins and survey-based research. If it seems to go over well over here, then I'm guessing a ride will be rolled out. As to the whole miniland debate, I think the solution is simple...just make one huge anchor ride utilizing every major Nintendo character and then a bunch of smaller rides surrounding that can be themed individually, in one all-encompassing video game environment.