In my own opinion I would like for Nintendo to make another Zelda game for the Wii with the same/better graphics as Skyward Sword. Lets be honest, the graphics were stunning and even though a lot of people didn't like the graphics or that the game didn't reach its full potential I think it was spectacular. As for the whole love interest thing I would like for them to at least make it a bigger part of the game. In a game sense I would like to see more Link and Zelda romance, but in reality if they kept getting together in each game it would be keeping it in the family. I honestly think that Link and Zelda may stay long time best friends, but their love interests differ. Zelda is royalty so her father would probably want her marrying a prince rather than a commoner (who happens to be a hero). Link would probably meet another girl, fall in love, and have kids while at the same time protecting Hyrule and the royal family. In my mind it makes sense. That's why Link and Zelda are always together, but not romantically.
As for the motion controls I did enjoy it, but at the same time I hated it because if you weren't close enough or have the remote pointed straight your movements would go all over the place and as the batteries deplete the movements become harder to control (at least for me it was). I would like for them to give us a new use for the motion control though. On to the number one topic of Link speaking I don't think I want him to speak because it is just something that makes Zelda unique. A lot of games these days have voice actors or even the option to pick what you want to say, but as for Zelda as the series evolves the continuation of Link being quiet just makes the game better. It leaves a lot of what he would say in certain situations up to the players imagination.
If I had any guess as to who the character from the past would be I would have to say either Navi, the Happy Mask Salesman, or Skullkid. My reasoning for each of them are the following:
Navi; had been with Link through the entire Ocarina of Time game, but for some reason she left as Link locked the Master Sword up. Why did she leave? It honestly made no sense to me. The Deku Tree was dead and she was Link's partner. The only other reason she would have to leave was to become an adviser for the baby Deku Tree because he's a tree so he can't move, clearly, but maybe she could be his messenger. Or you could look at it in a dark way and you know maybe it was just her time to go and she knew it so she went to the forest, but I don't think that was the case. I want to know why she left you and maybe she'll have this awesome story to tell us.
Happy Mask Salesman; He was a very mysterious character and I feel like they could use him in a lot more games. In Ocarina of Time he was just a mask salesman, but in Majora's Mask he managed to find a mask that had disappeared from this world, including the entire tribe, that could destroy the entire world. Clearly he has some sort of powers, but we never figured out what it was. I mean come on during the end he vanished in to thin air. I would really like to see more of him and maybe get the story on his past, who he is, and maybe even a little inkling of Ikana in the story as well.
Skullkid; Well first off her nearly got the land destroyed by an evil possessed mask that created a moon to wipe out the world. Now moving on I think Skullkid may have a return in the next game because the skullkids are very mysterious. We only learn they are their because they went in to the forest and became them. Nothing else was touched on them even though every other race were. I know a lot of people would say Midna because of the way Twilight Princess was left off and she may be in the next one, but I don't think they would bring her back since nothing else could really happen to Twili or her, but this is Zelda so I may be wrong. Back to Skullkid he was very interesting because he was the only one who would interact with you and somehow he managed to find his way in to Termina and got included in to the story that Anju's grandmother told you. I want to see more of him in the next game.
As for the villain I would have to say Ganondorf because in Skyward Sword Demise mentioned that as long as Link and Zelda live he will always be their to try and destroy them.
I'm basing all of this off of the possible rumors that you mentioned and I'm sorry if this is jumbled up or some of the stuff doesn't make sense, but I tried my hardest.
