Unpopular opinion here :

We don't need a new healer. AST and SCH cover everything healing has to offer in FFXIV. And WHM is off that, but they promised a re-work. Anyway, if they want to keep healing as Shield vs Regen and soft buffs to the party, AST SCH and a topped up WHM would be enough.
Just like past a certain point, we won't need new jobs outside of the novelty of playing something else, because what we have covers what we need.
However, if they were to change the gameplay, maybe it would give more room to new jobs... or just to rework current jobs.

I feel that right now, any new job is just for the sake of it. Yet it's new content, so we give it a try regardless. I'm worried that too much jobs will eventually make it harder for them to feel original. While a tweak to the gameplay itself would open doors to these implementations.