UPDATE: According to Cory Stockton (who hasn't lied before, and has screenshot proof), a new battle pet will be found in Northrend in 5.3 - a baby/mini Valkyr:
It looks fantastic, and it seems to be using the Tyrael's Hilt pet skeleton. (It's not a downsized Valkyr model as you can see. Stoked!
So.. your thoughts? I think it's a great addition, and I can't wait to have my little mini Northrend 'spirit healer' with me.