I think they will reboot it before they have to make a TES game in an interesting province. (My money is on Highrock next, and possibly last). Mind you I'm a pessimist by nature... and regarding Bethesda, a pessimist by experience. But it makes sense to me. Lets say they do reboot TES. OK, might as well make some good of that.
What cannon would you change?
Obviously most of the "what cannon would I change" would be a big list of how to introduce and represent more varied and unique culture and locales into TES, so aside from that, here's what's always irked me in TES cannon:
The Khajiit belong in the frozen wasteland, while the hairless and shirtless belong in a warmer climate. The Khajiit have fur for a birthday suit. It always bothered me how they complain about the cold wearing clothing on top of fur while next to a naked human. Granted they grew up in a warmer climate they would still not be accustomed to the heat... I really doubt any sapiens that come out of such arid badlands would not lose their fur like humans did in the same environment. When they finally do get to Elsweyr or it's equivalent, I hope they research the layout of old desert settlements and things like wind catching towers and the primitive AC you could accomplish with them. Ancient civs were pretty clever, I'd assume other sapiens would come up with similar solutions. Granted foreign architecture=lostsales or something to Bethesda, I hope they at least come up with something clever and logical in cannon involving magicka.
Before I derail my own OP:
There's a bunch of magical maguffin stuff from older games that are lost somewhere or conveniently never mentioned again.
Given the chaotic nature of multiple planes, deities, and the like, there's room for lots more "lost science/technology" like the Dwarven disappearance we already have, maybe a more definitive "dark age".
There's practically nothing on magicka itself, as in, readable spell books with imaginary pseudo-physics and laws... lots of opportunity for more exposure of the mechanics of it with new or modified cannon. There's even a gag character in Skyrim, a genius court mage deep in thought whom I swear is an intentionally self-aware parody of the non-nonsensical hand-wave nature of the current magicka.
What would you retcon?