One thing that has been irking me a little... nowhere in any promotional material have Abilities even been referred to. Not a sentence.
I don't know if we should read too much into this. Perhaps they aren't going to add any new Abilities, figuring that we do fine with the ones we have already. Then there wouldn't be necessary to make any fuzz about it. If you're going to NOT introduce something, best be quiet about it for as long as you can.
A second, though less likely, option is that they might be rewamping the entire system. After all, most Pokémon already carry three different abilities, though some are still stuck with one. Might be that they want to even things out for everybody. Then again, you'd think they would have mentioned it by now.
Adding more abilities to the game, like they did in generations IV and V, would necessarily give the developers two options:
1) Keeping the limit of three optional abilties per Pokémon. In other words, no Pokémon currently having three abilities will get any of the new ones.
2) Increasing the amount of possible abilities per Pokémon to four or more. Then again, that would make mono-ability-Pokémon (such as those with Levitate) even more "left behind" than they already are.
A third option would maybe involve reducing the number of options, i.e. removing or swapping some possible abilities on some Pokémon. I don't think this is very likely, though. Either way, abilities seem to be "piling up" for every generation now. I wonder if they will do something about it, or keep adding abilities to Pokémon for the foreseeable future. It will be exciting to find out.