I was reading the forums and stumbled across this little gem: http://us.battle.net/wow/en/forum/topic/10160426120#6
A poster asked if cross-realm heirlooms were still being worked on, and Bashiok said:
We’ve talked a bit more about our plans in recent interviews. We’re working on some ideas to get things like tabards and heirlooms out of inventory slots, as well as “toy-like” items, in a way that’s similar to pets and mounts. Soooooo, yup!