I don't see any other threads like this so I guess I'll be the one...
At time of writing, this is on the front page of MMO-Champion as datamined information from a new patch.
So, what are we looking at? Legit hearthstone client in WoW? A fun doodad decoration to be scattered across inns? Possibly one of the toys given to people who participate in beta (a Hearthstone version of the train kit? >.>)