Blizzard just posted that all you need to do is simply log in to receive the chopper (presumably in the mail) upon WoD release.
I was expecting the chopper to be part of a gold sink or an engineer plan, but it's free, can't complain I guess.
I'm on hiatus at the moment, but looks like I'll need to log in before sept 30, hopefully 6.0 will be out before then.