DotA 6.79 AI won’t be realeased soon
It looks like the developers that have worked to the previous DotA AI maps have retired. You can check this topic from the official playdota.com forums (you need an account to access the page).
Taken from that topic:
“The 6.78 AI farewell, will be the last map for the next 3 years I guess. Someone should re-code it because I tried looking at the code, I have no idea of the declared variables and without the knowledge of the makers of “farewell”. I think it will be really farewell as for now.”
There has been a few months since the last AI map was released (January), the initial developers haven’t said a word since then. There are a few raw maps posted on the official 6.78c AI forum thread that should be used for further development.
You might find some 6.79 AI maps on the web but those are not recognized officially by the community and they might be full of bugs.
The latest AI map is DotA 6.78c AI v1.4e, you can download it from here.