Tank and healer will probably be the two next jobs for 5.0 to balance all the existing jobs.

BTW, at the announcement of Heavensward I thought that the MCH will be a dual-gunner job. I was so hyped.
Finally I didn't play it often. Musketeer exists on FFXI and it's a dual-gunner job, so I hope it'll be introduce in the future. It'll be one of my main jobs for sure !