Initially there will be mainly bug fixing and performance tuning.
We have tested the data packages under Steam, but apart from some minor technical issues Steam has with such large DLCs it's also problematic on a different level. The problem is that the full dataset in the same resolution that you get now progressively downloaded, 40/20 meter data (or 20/10 if you enable it) would be 172 GB (resp. 350 GB). That's quite a lot to download for an unknown game for new users. Including just some reduced resolution data would make it uglier, again not something attractive for the users.
For now we've set up a dedicated server for the data that should be providing a much better download speeds than our previous one. We assume that once we put it on Steam, the installation will include data for several startup locations in full resolution, and the rest will be downloaded dynamically. For people that really want to have the complete dataset there will be a separate DLC or two with the full data.
Anyway, a Steam release needs to be much more polished and playable for the common user, and we also have to address some woes with AMD GPUs and drivers first.
Currently we are working on several things, like characters, interactive cockpits, AI, road & rail editor etc, all needed for possible future games made on the platform, about that - later.