Early Access & Account issues (PS3)

[Trombe]

So here's my question: If I do this and it's successful, does that mean that after the official release I can go back to my old PSN account to play or am I stuck playing on the EU account forever????

According to the instructions, you are going back to whatever original account you normally use.
This is running under the assumption that the account binding process happens when you launch the client, not when you put in the redemption code and download it.
Basically IF this works, you will be able to use your NA account.