I could see anywhere from 16-32, but I doubt it'll be any higher than that. Ram has kinda slowed down in development (as have CPU's), at least from what I've seen these past few years.
Made a bet with LipeJJ and HylianYoshi that the XB1 will reach 30 million before Wii U reaches 15 million. Loser has to get avatar picked by winner for 6 months (or if I lose, either 6 months avatar control for both Lipe and Hylian, or my patrick avatar comes back forever).