Okay so before I get started let me just say Skyrim was one the best games I have ever played and I thoroughly enjoyed every second of the experience and I'm not even close to done. Now that we've all experienced Skyrim we're now waiting so patiently for TES VI and we have no clue what you guys are going to do with it but since it hasn't been announced and these forums are for open suggestions. Here's some Ideas and Suggestions I think would make TES VI History making.

1. A more dynamic AI for NPCs, as much as I loved Skyrim I was a little disappointed with the AI. I spent hours trying to get that mechanic were you drop an item and people will either. Fight for it or give it back to you. I also didn't like how there wasn't much variety in NPCS or Voices they all seemed the same to me.

2. The game should be set on the entire Tamriel continent instead of just one province. Countless times in both Skyrim and Oblivion I felt strong disappointment when I ventured to the edge of the map and couldn't crossover to the other side. For too long I have waited since Arena for another Elder Scrolls game which would allow us to go everywhere instead of being limited to one province.

3. A dynamic weather system that depending on the province you are in, the climate of said province would effect the gameplay. Example:
If your in Skyrim and your character isn't a Nord then you need warm cloths and food to survive the cold wintery climate or you could use a spell or an enchantment that allows you to resist the cold entirely. Same thing would apply to other climates like Deserts, Tropical Forests, Swamps, ect.

4. Creatures and Animals vary depending on location.

5. Dragons, Oblivion gates should return and the games plot involving the return of Dwarves as well as Dwarves being a playable race.

6. Marriage should be continued in this game but this time with more benefits. With the option to have kids or get a divorce.

7. The game starts in the province according to the race you pick.
You pick Imperials you start of in Cyrodiil,
You pick Dunmar you start of in Morrowind
You pick Argonians you start of in Black Marsh.
You get the point.

There's a lot more suggestions and ideas but I think those are my personal favorites.

It requires way to much manpower these days to do the entire province. If the Dwemer return, there will be no more mystery. The TV show Lost was better before they revealed who "the others" were.

@Luke Skyrimmer, Well think about it by the time TES VI is even announced the PS4 and Xbox 720 and extremely powerful PC Systems will be released giving game developers much more technology and capabilities to makes games exactly how they want. So I don't think that would be a problem for Bethesda especially.

Ideas and suggestions for future games belongs in http://www.gamesas.com/topic/1311878-official-beyond-skyrim-tes-vi-4/. You're welcome to repost your ideas there.

Better technology won't help much with generating large areas, the locations found within, and the NPCs living there. In fact Daggerfall managed to do a huge populated area fifteen years ago.

If Bethesda were to double the space they'd need twice as many artists and designers. To do the entire continent would likely require ~10 times the design staff. It also introduces many new complications concerning balance and what not. New tech may allow the game to keep track of ten times as many NPCs and items and what not, but unless MS and Sony really ramp up the RAM support for the next generation this may not be true.

Unless Bethesda scales back the detail, or limits you to specific locations, doing the entire continent just isn't feasible.