I think hey were waiting for Scorpio, but Microsoft isn't allowing games to be targeted specifically for the more beefy hardware - at least not yet.
The original one might not be burly enough for the game after all.
Either that or they prioritized DLC for the current platforms, perhaps in response to lukewarm response since the announcement.
Or they are just silently toiling away on the content until release time comes.
If they can e.g. get mod support but must wait on a few updates from Microsoft first, it's possible they are holding on for some platform features as well.
At any rate, I am interested in first-party updates on this front as well.