As Enkidoh said it's very unlikely there will be a sequel MMORPG, and if there is it's unlikely to be like anything we're used to given how the genre itself is constantly cannibalizing itself. Whether we like it or not that's just how the current market trends are going - and if MMORPG's do see a resurgence down the road they likely won't be much like their current iteration. That's not to say the genre is dead per say, but the years of MMORPG's being the 'big thing' for companies to capitalize on are long gone for now.

With that said however I can absolutely see FFXIV receiving homages in future FF titles. But that's pretty much it unless SE decides it really wants to dip into spin off titles or secondary media like comics and books.