Geomancer does seem more plausible than a Blue mage at this point, but I love both jobs.

The reason why I think Geomancer is more likely is just because there's more freedom for the devs to mold it into something they want. I know quite a bit of people see Geomancer in the way the Tactics series has utilized them (terrain and weather nukes), but recently in XI and Final Fantasy Explorers they've played-up their ability to set fields and other ground-based effects for either buffs or debuffs and focus a lot more on divination and feng shui aspects of Geomancers. Of course, since there is no pure-support role, they would need to be careful on how reliant they are on buffs and debuffs should they go that route.

The way the game is now, Blue mage could turn out incredibly boring without shaking up the status quo.