For the last few years, I have had several ideas that I would like to see in the next Zelda:
As other people have mentioned, an overworld with more life in it. Zelda II had several villages with tons of people in them. Since then, we've only had one or two. ALttP had Kakariko and that's it. OoT had Hyrule Castle and Kakariko. MM had Clock Town (there was another one right? my memory is failing me). WW had Outset Island and Windfall (and maybe you can count Dragon Roost). TP had Ordon, Hyrule Castle and Kakariko again. But that's pretty much it. No life outside the towns and not much inside them either. I'd like to see people roaming about the overworld, some of them fighting monsters, some of them fishing in the streams or hunting. Maybe even some of them living there in huts.
Secondly involves how the dungeons integrate into the world. I'd like to see them more seamless. Not so much like you're halfway through a dungeon before you realize it kind of seamless, but perhaps with areas where you go outside and can see the rest of Hyrule around you. Much like the Skull Palace from ALttP, you can leave and re-enter the dungeon at different points. My other idea for how dungeons would integrate into the world is that when you finish a dungeon, instead of leaving the way you came in, you exit from the Boss room into a completely new area of the overworld, such as a new village perhaps. Later in the game after obtaining different items, you can warp to that town (or ride puffy's dragon lol) and re-enter the dungeon. Once inside, you'll find an area that is unlocked with your new item and it becomes the next dungeon.
There's a few other ideas I've had that I can't remember right now.
