Has it been confirmed its just Mario and family (Luigi,Peach,Toad,Bowser) or is Zelda still a possibility? If they go outside of the main Nintendo family I assume that would be where they go. Ocarina of Time is still considered the best video game of all time by many. I hope its represented in more than the gift shop...
The initial project is 100% Mario. Mario Kart and Donkey Kong coaster seem to be all but confirmed, and there's a good chance (IMO) that ET will be replaced by the Yoshi ride coming to USJ.
AFAIK there were also plans, early on, that had other franchises represented as well. Those don't seem to be in the cards for USF, but that doesn't mean they won't pop up in the future whether it be in Park 3 or elsewhere.
Technically nothing has been confirmed yet, but unofficially confirmed by @Teebin as definitely Mario Kart and Donkey Kong, with something (I forget what, mind his blanking but I believe Yoshi) to possibly replace E.T. in a future expansion (but this is definitely not unofficially confirmed, @Teebin just mentioned that Japan is getting this ride so its possible we may get it eventually)
This. I've heard constant whispers that ET is on the block, so personally I think it'll happen. Whether it happens with the others or as a Phase II is the question for me. I think the latter is more likely, if only because they need all the capacity they can get so it make sense to close ET later.