Personally they dont typically start advertising this far in advance for simple missions or updates, which leads me to think its an actual faction, some sort of new mini faction or at least something very significant and out of the norm, that they want to generate some buzz for.
dstahl has said 2013 will deal with new factions and how they are implemented so its possible this will be part of that. at least in some way we should see some movement towards a third faction this year. the may update may just be phase 1.
they also said season 8, which they are not even really calling season 8 is their biggest update by far and is more of a true expansion, which suggests something a little more than just the standard FE.