I imagine they won't add new wards on Aether/Primal/Crystal until most if not all wards are full on Dynamis, as adding new wards to those older data centers all but guarantees that more people leave Dynamis because its literally only good for having plots, hardly anyone plays there for any other reason (in fact most of the players there are literally just housing alts, they don't play the character otherwise).

But that's probably not going to happen any time soon so long as veteran players refuse to transfer (and there's plenty of reasons not to) and new players keep funneling into A/P/C to avoid being stuck on a "dead" server.

Square-Enix would need to either implement a cross-DC party and duty finder so being on Dynamis isn't agony and maybe more people move there (a feature which could take years to create) or they would need to just give everyone instanced housing, where limited wards only matter to those who care to show off their home (but good luck getting SE to budge on their whole "but neighborhoods" thing).