They left it open as to whether some of the phantom jobs may become real jobs in the future. Some of the phantom jobs are already playable jobs, like monk.

But I think geomancer as an actual playable job is unlikely considering we know it has no job stones and the AST questline confirmed the job is just a far eastern meld of conjurer and astrologian and the encyclopedia doubled-down on it. The only person in the world who knows how to be a geomancer only unlocked all aspects of it in another job's questline and he casts conjurer spells while geomantic barriers are perfectly integrated with astromancy and it turns out that astromancy is itself the final key to the job.

They kinda wrote themselves into a corner if they wanted to make it an actual thing.