From what i've read, all add-ons must be approved by Square before they can be used, not sure if that implies an ingame interface for adding them or what (mostly because i heard that the same add-ons will be on playstaions too). That would mean that even if the means to make them is out in six months, there might be some delay in them actually being out, depending on how quickly Square approves them.

There is still the live letter part 2 for 2.2 to see what might come, but it could come later too, 2.3 or so. They haven't said much, but with one of the parsers now having more things that broach hacking, they might be making sure nothing like that creeps in.