Quote Originally Posted by Sobia View Post
Just log in with your SE account on the PS4 (when you can). It should give you a list of characters you can transfer. From there just select which one(s) to transfer and you're set (but note you can't play with them on PC once you bring them over to the ps4).
That's not strictly true, that applies for people taking the upgrade option where you won't have access on a PS3 once you transfer. For the OP's question he should be able to use the game registration either on the console or via the mogstation which would allow his account to be played for either platform.

In the upgrade instructions it mentions that anyone that wants to play on both the PS3 and PS4 would have to buy separate copies and register against their accounts (instead of taking the upgrade option).