FFXIV will last until the next good mmo is released that draws the attention.

XIV is a themepark, so it will do well until a better themepark is built. There is not much stay power in XIV in my opinion, but there is nothing besides this that has been this polished and featured since WoW launched.

From the looks of the genre atm... it will last awhile because most games are being made by Indy companys who have 1/100th the funding needed to make a good full featured mmo. Genre is dying, Yoshida is right. But it is not because players do not want mmo the devs of the mmos are feeding the genre poison and wondering why it is dying off slowly.