I feel like (and hope) that if we get another healer it will probably be the Geomancer, since it's a big part of the Astro storyline and had an interesting, characterising mechanic with the whole "what terrain are you standing on" thing. Also, White mage seems to be moving away from it's earth/water/wind schtick now and is becoming much more "holy" in its aesthetic so I think that might be Yoshi-P's way of slowly changing the WHM's identity so that it doesn't feel too similar to Geomancer? Idk this is just me speculating.