and do you guys think itll be possible for some one in dawnguard to be a werewolf?

Most likely it will be possible. No way of knowing now though. Oh, and yes, there are screenshots of the werewolf perk tree. Confirmed.

There is a Werewolf perk tree in the DLC and one of the Devs mentioned that he played as a Wolf and flayed a Vampire Lord so it shouldn't be a problem if you join the Dawnguard as a werewolf...

Them Werewolves have come a long way.