I just want my sub-races for the Khajit and the other ethnicity of the Bretons
I hope we'll get to see that some day, but I fear it won't happen unless we get a game set in Elsweyr, where logically, Khajiit would need to be given a lot more attention by the developers than they have been in past games.
Other than that, I could see Falmer appearing in Skyrim, though certainly not playable, of course, it's also possible that they'll be like Ayleids and Dwemer, where we get some lore on them and see their ruins, but don't actually see any living ones (Okay, we saw one living Dwemer, but he was a horribly bloated thing that can only move about on mechanical spider legs. We didn't see any living Dwemer that were as they must have been when they lived long ago, although the statues and Dwemer ghosts in the game probably gave us a good idea of what they looked like.) but I doubt we'll see Sloads or Imga or anything. And any of the Akaviri races would likely be saved for a game where Akavir got central focus in the story, like if there was an Akaviri invasion, maybe in the next game, or some future game. In any case, it's already confirmed that the playable races will be the same ten we got in the last two games, I believe, and any other races we encounter will likely be not playable, if they're not just counted as "creatures" by the game.