I can't speak for the devs, but my personal view is that ZK still needs a lot of work on the new user experience before we start pushing hard for new users (i.e. releasing on Steam and - hopefully - having an accompanying PR campaign). It's come a long way recently, much better than it was even just a year ago, but more is still needed.
I'd break that work down into three areas:
- User interface (both in-game and lobby)
- Tutorials / guides / learn-how-to-play
- Single-player campaign
People are hard at work on all of these areas.
The game itself, including the AI, is more than ready for an official release and a PR campaign.