From what I've seen with Square's recent games, the only one with DLC that I waited for the PC version for (Because it made me want to RAWRRRR because it was so extreme, there was some story hidden in the DLC) was FF13-2. SO FAR, they haven't done another FF13-2 DLC wise.
With Lightening Returns, it was costumes that were DLC. And Square seems not to put in true microtransactions very often in their RPGs (I've only seen that in one game, and that was Bravely Default, and you could duck paying for it if you were patient) other than bits of DLC. I think they learned their lesson on FF13-2, but we could see some paid dlc in 15 and KH3. Let's hope it's just alternate costumes or something like that. ^^ Or like the cash shop in FFXIV; you don't have to buy that stuff, and I haven't bought anything from there, I just pay the monthly fee..