When it's going to come out is anyone's guess. I think they're still trying to beta-test it, frankly. Supposed to be for that third update, but, as of now, they schedule it at, at minimum, late November.
It sounds as if they finally admitted that the present Augment system is one masterful flop, as they've introduced the Evolith system (and all-but explained what the heck that huge data update was from last week...).
Basically, you can now slot your own augments of choice, if you can get the stones you want, into just about anything -- which, of course, raises the potential for another side effect (encouraging players to augment (and, hence, render Exclusive) their entire gear set, yanking the whole mess out of RMT's hands).
Mayhaps that's the entire point of the Augment (and now the Evolith) system, and something they might be considering for XIV.