In order to play the game on a system you must have a registered code for said system tied to your account. When/if you pick up a PS4 and you get the PS4 version, you will again need to buy the game for that system so at that point you would have PC, PS3, PS4. If MS changes their tune about Cross-play servers, you can likely expect to see an XB1 version of the game (but only if MS changes their tune, and not until then.)... The greatest thing about the PS4 version: PS4 has built-in-Twitch app for streaming your games.