Noone knows, I honestly doubt even the devs know yet. A lot will probably depend on what publisher, if any, they go with for NA launch. They are apparently still looking for one.

If they self-publish, you will probably be able to use same account and not re-buy the game.

If NA gets a seperate publisher, like Atari for example - you will probably have to use a new account. However, that doesnt mean that it will have a fee per-se, and will probably not be a 50$ box like AoC if that happens, but be available cheap as a digital DL...

This is all total conjecture, but still a likely scenario.