The materials released so far indicate that the way to get your Pokemon from ORAS and XY into Sun/Moon is through the Pokemon Bank, which is going to be updated. That suggests to me that trading between ORAS or XY into Sun/Moon is not possible. I understand that they didn't specifically say you cannot trade, but it's not unreasonable to conclude that you cannot trade between XY/ORAS and Sun/Moon. Otherwise, why go out of your way to mention Pokemon Bank in relation to XY/ORAS and Sun/Moon? If we're meant to think that Sun/Moon are the same generation as the current 3DS games, it would be understood that you'd just trade between versions as always. Having to go through the bank clearly indicates incompatibility between versions. That, on top of all the other clues, indicates that this is a new generation.
Now, I'm curious what this means for Pokemon Bank in relation to XY/ORAS. Once they do the Pokemon Bank update, will we be able to move mons from the bank to XY/ORAS? Or do they become next gen mons if they're in the account after the update? Will we then be forced to use Pokemon Transporter to upload Gen 6 Pokemon into the bank after the update? In the past, the move of your old mons to the new gen games was a one-way trip. Even with Pokemon Bank, I'm guessing that will still be the case--though that's just a guess.