They replied this on the forums just a moment ago with some insight to the priorities they are working on right now.
TLDR: All hands are on deck for the release of the expansion Bridges & Ports; after that works resumes on other things.
Outakes:
Unfortunately, the Asset Editor related work has had to be pushed to the background while we have been focusing on other priorities. After the Bridges & Port related work, we will have the team tackle the remaining issues, and the asset editor for buildings will be released as soon as it’s ready.
The plan is currently to support building assets (and props) and expand the supported asset types in the future. Once we have established basic support for assets in the Editor, more complex asset types, such as vehicles and networks, can be worked on.
We’re currently working on:
Fixing the issue with too few resources produced by offices being consumed, causing office company worker counts to drop to the minimum amount.
Updating the production panel to provide a better understanding of the production and consumption of resources in the city.
Rebalancing resource consumption to ensure all companies work as intended.
Improving the water simulation and updating the maps to ensure they have water outside the playable area.
The reason we still call PDX mods beta is because the asset editor is missing, is not really any features related to PDX mods, its just to set expectations on modding in general.
More animations and updates to citizens are in the works but we do not have an ETA for when they’re ready for release. Similarly, bicycles are planned but on hold until Bridges & Ports is done.
Priorities after the expansion is released: Bicycles, Asset Editor, and more bug fixes.