Hearthstone Beta will have a reward for WoW players who get in (The Hearthsteed). It is also expected to start by / in summer.
WoW 5.3 will launch on 21/05/2013 and will include the Hearthsteed mount. The first technical day of Summer will happen exactly 1 month later (June 21st)
And with the game at least appearing to be in a totally functioning state... Well, do we think Beta is getting very near?