Looks like I was wrong. ;)
You must have seen the Pandaren Brewmaster Mini-pet by now. The model has been datamined in 3.2.2 and looks awesome. Don't take my word for it though:
So, where will you see this? Well, it won't be for the 5th Anniversary, we're getting the super-cute Onyxia Whelpling to commemorate that date. It's unlikely to be for the Brewfest either, the holiday is awash with pets, mounts and a title already. Plus the first load of Violet Protodrakes are due. But still, a Coren Direbrew uber-rare drop (al la the Scorchling) is not beyond the realms of possibility. However, I think there's a better bet.
The World of Warcraft Magazine.
Blizzard are very good at incentivising real world purchases with in-game rewards. Just look at the TCG, you can be sure that if the Brewmaster was a TCG reward Upper Deck would be proclaiming it from the tallest tower. The only upcoming event as yet not accounted for is the release of the first issue of WoW-The Magazine, also due some time around WoW's 5th anniversary, and the enthusiasm for it has been muted to say the least. This would be one way to get the manic collectors salivating.
So, a cool mini-pet for the $39.95 1 year subscription. Tempted?