Pretty sure they said a new story would be starting after EW- which likely means another ten years. Now, in ten years it'd likely sink in the limitations and such of FFXIV, and I could see them doing another mmo then- but for a 2023 release for an mmo, they'd have to have started 2018'ish... I really doubt even Yoshi P could be making ShB, EW, FFXVI AND a full new mmo at the same time. If he were to make a new mmo, I think that'd take all his attention, and he's really only able to do FFXVI at this point because the departments under him in FFXIV are probably very autonomous by now.

I'd think it'd likely be 2030'ish, and I also imagine they'll want a new vision, so he may end up mostly consulting rather than being in charge.

FFXIV just hit the height of its popularity, and honestly has no competition right now as other big mmos (ESO, BDO) or upcoming mmos (Ashes, New World) are vastly different and capture different audiences- of all the times to make a new FF mmo, this is pretty much the worst possible time.