Hopefully Cam but you need openers who can bat all day and and then some
That's why Warner & Rogers worked so well, there was one of each. I can see Hales and Cook having a similar dynamic (if the pairing is given a chance to develop!)
Nick Browne of Essex was the best opening bat I saw in county cricket last year. Which is not to say I'd have him in my England team right now; but I'm not overly confident of how Hales will do.
The England openers spot seems to be something of a poisoned chalice. I think the added pressure of knowing you'll be getting two series (at most) where you have to make the spot your own is detracting from people's natural game.
If Hales doesn't prove to be an instant success I hope he's given a fair crack of the whip (but nobody else has been, so I can't see it happening...)