Pandaren Fire Spirit - BoUYou may be wondering, 'There's fire, spirit, and earth, so where's water?' Well the Pandaren Water Spirit already exists, and only the PTR datamined finds are listed above. The water version was added in patch 5.0.4, but was never released.
Pandaren Air Spirit - BoU
Pandaren Earth Spirit - BoU
Clock'em - BoP
But hopefully it will be soon! Along with the other three elemental spirits. :)
It's great to see another mechanical companion possibly coming soon, although I'm half expecting a clone of the Clockwork Gnome. If it's not and the Clock'em pet is a whole new model, then great! If not, then oh well. A new companion is a new companion, and old model or not, it won't stop me from collecting it. ;P