If you look at the FAQ it explains that it will be done when its done. Its hard to actually do an ETA when there are a lot of factors like what's going on with stuff outside of making the game or potentially an idea that has alot of complexity to it (Deoxys). The one real thing I can say because I'm not the creator is that hopefully the gap between the Hoenn update and the next update is shorter then the gap between Johto and Hoenn updates due to Sinnoh being split into 2 parts