As great as their legacy has been, I don't think Final Fantasy will regain its RPG domination like it did in the early 2000s. Final Fantasy has always had well written stories and great voice acting for single player game play. But with the advent of MMORPG, its difficult to see Final Fantasy surpassing the MMO juggernauts.
The question is that FF MMOs ain't focused on surpassing or being the TOP Played MMO, they're designed for a specific amount of players or whoever likes these games. Spoiler For example, I know that WoW is one of the TOP games since 2000s, it has a vast amount of content, one of the best PVPs I've ever experienced and an awesome story. Yet I can't stand the combat system being shallow without the flashy effects, it makes the game feel dead...
Hmm, who's on top of the RPG genre anyway? I think that there are a lot of developers who are looking into the RPG genre that it's hard to get to the top. During the SNES and PS 1 days, Square reigned supreme. But I think that Square is continuing to evolve as an entity. It started with FFXI. I don't know why they're still trying to get into the MMO market. Is it more lucrative? Probably. But in order to get to the top, I think that they should go back to their roots.
As much as I would love for them to go back to their roots, but I don't think they will their is too much competition for them and why go back when they can make more money by making P2P MMO's even if they are bad the die hard Final Fantasy fans will still pay the monthly.