Depends really, hopefully SE will use the entry requirements on the bare minimum to effectively complete the instance. Meaning you could get into CM, Praetorium, and WP (maybe Ifrit and Chimera too) with questing gear and maybe full AF.

Next tier would be AK and definitely Ifrit and Chimera.

Then Garuda and Hydra.

Then Titan (also CT from what I've read).

Then BCoB and the new primal extreme instances.

Of course this is purely logical assumption since SE could take this any number of different ways.