Zelda Begins: This story is detailed a good amount in Hyrule Historia in the manga section. I won't spoil it if you want to go read it for yourself but it establishes Link as kind of an "Aladdin" type figure to begin with (he committed crimes and was pretty 'not so friendly' in his first "incarnation"). I think having a game (or even a series of games) based on this early ruthless Link could be a way for Nintendo to introduce a new type of game. They could use different gameplay models since this is the origin story that takes place prior to Skyward Sword. I could easily see it being more Prince or Persia/Darksiders like since this is prior to him having all of these legendary items that won't have been created yet. This game would have an amazing mythological aspect to it as well since this is essentially exploring Hylia (*SPOILERS FROM SKYWARD SWORD***********************) becoming Zelda through a sacrifice. Another amazing thing this game could do is explore the 'old gods' that "left." What exactly happened to them? Why did they leave? Are they vanquished and if so by who? Are they on a different world? Could we eventually explore this other world?
Zelda Ends: This is one of those ideas I have that I personally love but I think it could potentially cause a lot of controvesy. I want Nintendo to make the last Zelda game. I don't want them to stop making Zelda games, though. What I want is for them to find the end of this Zelda/Demise arc. They can still make games that reference things that happened BEFORE this game (so, hypothetically, they could make another 40 zelda games that are all amazing that take place BEFORE the Zelda ends game). But what I want is for them to finally figure out a way to destroy Demise permanently (Ganon and all his other incarnations) and I think the most fitting and emotionally pulling way to do it is to make Zelda (Hylia) herself sacrifice all her 'life force' to permanently destroy Demise after she has spent eons barely holding him back while the people of the world suffer greatly. This would permently kill both Demise and Zelda and leave only Link to be constantly reborn into the world. This could open up a whole CAN of goodies in terms of where they could go next (Where would the two pieces of triforce go to now? Would Link control them at all times? Will other villians arise that would try to take control of them? etc.).
*EDIT (it submited it before I was done...)
Zelda Fusion of Time: I think it would be AMAZING if Nintendo made 3 Zelda games all in the three timelines over the next 10 years or so that all (at the very end) reference a connecting point to the other two times lines, then Nintendo could make one game that literally connects these three games and their three timelines and finally reunites the timelines. Undo what was created with Ocarina of Time. It could be amazing! You could still make games that take place in the three timelines that would just be prequels to this game, but then you could seriously explore the future instead of parallel presents.
Zelda - 2d: I want Nintendo to make a 2d game for the Wii U or whatever comes after that is in fully glorious HD. I want it to look amazing in 2-d, with 3d cut scenes that are beautiful. I want it (due to it being in 2d with much less being required to display everything) to be a RIDICULOUSLY long 2-d game. I'm talking 80-100 hour campaign that AT THE LEAST quadrupils the length of "Link Between Worlds." I want this game to be one that I literally play for 6 months trying to beat in my free time. I want Nintendo to make one more GRAND adventure (not one designed for handhelds...) ode to us old school gamers and I want them to do it in the longest 2-d action adventure game I know of. It would take forever to beat and it will be so glorious to play through! Typing this has me excited!!!
Paper Zelda - Why not get a little more light hearted with the series? This was rumored with Project Cade back years ago and I wouldn't mind it at all! This serious has a lot of humor in it. Imagine the fairy as a partner in rpg battles and Tingle as the master overlord enemy behind the scenes...!
Crossover - Star Fox discovered dinasours on a planet. Why couldn't he discover a medievalish society on another planet that has Hyrule? It could work people. It. Could. Work!