This is a pipe dream. At most it will be arcade and third-party games. Aaa titles are known to have timed and console exclusives (ex. gear in destiny, dlc for call of duty and the division) so having servers that intermingle would make these things unfair and restricting for one console over the other. You would have to get developers and the people publishing the game to agree to eliminating exclusives. Then you have console exclusives, if all the sudden you could choose what console you want based on console and not the exclusive games it will get, that could end up being bad for either Sony or Microsoft.