Wasn't it confirmed at some point that the Yokai Watch event is coming back, with new weapons for the classes added later? Could've sworn I read that somewhere.

Crossover events with other properties (Yokai, Dragon Quest, Garo, etc) naturally require the permission of the property's owners first, so that's at least partially out of the XIV team's hands. Not sure how that would apply to other Final Fantasy properties, but we can probably rule out the XIII event, since the rewards are on the Mog Station.