Pokémon X and Pokémon Y

How so? There are plenty of hints, more than those for a Hoenn remake or anything else, really.

I only really think it's unlikely for one reason. Because we haven't had a new type since Gen 2, and those were only really introduced because psychic was virtually unstoppable in Gen 1, having only weaknesses to Bugs (lol) and Ghosts, and at the time, the only ghost types were Gastly/Haunter/Gengar. It made more sense to add some more weaknesses than pump out like 15-20 new ghost types into gen 2.

I'd totally be up for some new types though, so long as they put plenty of thought into them. It's tough to think of something that would really add to the pokemon formula though.

Maybe something weak to normal (and bug, since bug moves really get screwed over, 6 types resist them, only 3 weak against...), but strong against dark/ghost types. (Holy/Light element?).

ACtually, now that I think of it, Grass/Bug could really do with some rebalancing., 6 resistant/3 weak to bug and 5 resistant/3weak to grass are pretty bad. Poison doesn't do that well either, with only grass weak to it , and 5 resistant/immune, but poison type shave generally been more of a status effecty thing anyway, so that's not as bad.