Maybe it's silly, but the fact that they are calling it Phase 2a, implies there will probably be a Phase 2b. They're trying to establish dose dependency right now. That's probably also the reason they want to double it from 1 injection FX-322 (3 placebo), to 2 injections FX-322 (2 placebo) and ultimately 4 injections FX-322. They also want to follow patients for six months because in Phase 1/2 after the 3 month follow up some patients were still improving.
My guess they will take this data to a Phase 2b trial (like the maximum tested dose dependency) and maybe expand to new patient populations, like the elderly (presbyacusis - also mentioned in their IPO).