At least it's how it worked for Desura. Everyone who bought the game via BMT got a Desura key as soon as the game has been release to Desura.
For Steam is should be the same, but as I already said, we will have to investigate into it. Maybe pasik knows more already.

Thanks! Where will you post when/if you get any more info on it?

here.

I don't know more about Steam yet.

I'm fairly sure it has similar ways of activation keys as Desura, at least I faintly recall reading of such things happening with some other games.

I can't be sure about this though, we'll know once/if RWR gets in Steam.