It's been stated by one of the producers and confirmed by Zorba that AddOns are slated to go Live with the 1.5 patch, which is due at the end of September or beginning of October. As we all know, however, sometimes things can happen that can change plans. So, fingers crossed, we'll see them with 1.5, barring any problems.
Source. Go to time stamp 23:15 if you just want to hear the announcement about AddOns. They talk about a lot of the other things they are working on as well, though, so it's worth watching all of it.