It's never too early to speculate, theorycraft, and anticipate the next jobs. The work for each expansion starts a lot earlier than one would often think. What jobs are you hoping for?

Personally I would like to see a new caster. Something that is completely unique from Black Mage, Summoner, and Red Mage type mages. Perhaps Time Mage, or Geomancer.

My other thought is maybe something else with an eastern origin. We only have Samurai, Ninja, and Monk for the eastern type jobs, and Monk is a lot closer to near east in origin than the actual east. Onmyoji, Oracle, or something else with an eastern flair would be a welcome addition in my opinion.