last time i heard from the pax -interviews, i believe it was not promised for 3.0, but shortly after. gonna look up for the exact words.

edit:
http://www.reddit.com/r/ffxiv/wiki/pax_2015_interview

Reddit: Here’s a question that’s asked a lot. What’s the current state of the API for addons?

Yoshida: We’re still in development. It will still take more time. We’re thinking maybe after the launch of Heavensward we may be able to give you a visual reference or a screen layout of some sort. Of course having to have patch updates go on at the pace we’re going at any additional side projects that we work on tend to take a bit more time. But of course we’re inching slowly closer to making it happen and we’re continuing to work on it.