An infrastructure overhaul of that magnitude will likely never occur. They are better off creating a brand new FF MMO at that point. We are seeing gradually deviations away from 1.0 code but a complete overhaul just doesn't happen to an active game. Citing that because FFXIV managed to recover once following 1.x's shutdown doesn't mean they can do it again without player revolt. Keep in mind, to the average player, nothing is amiss. Sure, they may want more QoL features but they likely wouldn't agree with temporarily shutting down the game or to have it remain without much content for an extended period of time.
At best, any significant changes such an infrastructure won't occur outside expansions.