So I heard that the starters dual types are going to be Fire/Psychic, Water/Fighting and Grass/Dark, which would be very interesting. I wouldn't bet on it though, since I'm basing this speculation on this image, the source of which I don't know, so it could very easily be wild speculation itself:
The grass/dark thing is especially tenuous considering it's not even alluded to above, though it would make sense if the other two were psychic and fighting, since it would function as a reversal of the old grass>water>fire>grass type superiority.