Seems like there is alot of information going around, which may or may not be true..,
I dont recall where I read that XVI had either the same core, or a branch of what XIV has but tuned for A SP game.(though this was likely speculation from some forumer, specially since it tied too well with the Graphics update.., unless.., it's cause XVI is as such, that XIV Could retroactively improve..,)
Guess we won't know til XVI releases on console..,(and people dare to break in and peek..,) and once more information on the update surfaces/is released.