not really, the materia system by and large canabalizes itself. There may be a few floating around but they wont be affordable, and in all truth, you know what you do to a 2xmateria when you get a 3xmateria? blow up the 2xmateria trying to make it a 4x materia.
even if one guy doesnt take that risk, some guy down the line will.
anyhow, the fact is there will be way more ifrit weapons, stronghold gears etc than there will be 3x materia crafted items, simply because the amount of resources required to make one are much more stringent than it is to get Stronghold gears.
See im confused, because on one side you say you want gear that will last a long time, on the other side you say you ll end up wearing your materia slotted gear forever.
in any case, it wont be forvever, whenever new slotted gear comes out thats basic stats are better, or more tailored to you liking, people will start to try to create 2x materiad versions of it. but their old gear will last them until they can finally create the slightly better version. It will still have value, because even if it isnt the best, its still better than anything you could easily obtain without massive monetary investment, or time investment.
Rare ex gear could only be slotted by a self crafter at this point, so its not that important yet regardless. Probably what they should do is re evaluate some of the lower class rare ex drops and put them as meldable, but things like ifrit weapons, cant would far outclass things if they had the same materia abilities.
they said they were thinking about it though, so i wouldnt say its impossible to imagine that they will allow it, or make the rare ex gears at least materializable, with some of them having special materia coming from them.
But i would imagine it would not be the best gear in game even so. If they allow great gear to be destroyable, and put in the loot system people want, then people will be competing for the same gears even when someone has gotten in 4 or 5 times. it will just make the elite that more elite, even within their own groups.