Looks like it'll be a new generation after all, based on the announcement that it won't be able to trade directly with X and Y or ORAS, only being able to communicate with them via Pokemon Bank.
However, they will be able to receive Pokemon from the Generation 1 virtual console games as well: http://bulbanews.bulbagarden.net/wiki/Generation_I_Virtual_Console_games_to_be_compatible_with_Bank