I see it from a company perspective as a flagship title game. They will need to spend money on it regardless of how they go about it.
Either they rebuild it as a solo RPG game that doesn't need servers so the title isn't simply lost to time, or they rebuild it so server costs will be negligible while keeping it a MMO.


This isn't a spinoff game or new standalone title that they could just get away with closing down servers and just #dead_game. That would break continuity of FFs 1~15 all still being available for play.
They have to choose how they keep this game around, not if they'll keep it around.