Could anyone tell me in which regions the retail version of Brink (pc) will be available? I prefer getting boxed games but if availability is an issue I might as well get some pre-order bonuses off D2D or steam.

By 'regions', do you mean countries? I think your best bet will be to query this with your local game-dealer as they should know their retail versions with pre-order bonuses by now. If you are in places like Africa, Australia etc. Then the pre-order bonuses specific to the country haven't been released yet and you might have to wait and see.

"By 'regions', do you mean countries?"
Yes. The local games dealer is clueless. Anyway, I have sent an email to Bethesda regarding this, will update on getting a reply.

BRINK will be available like every other game; I'm quite sure about that.

Unfortunately, that is not the case in Asia.