From the outside it seems to be in maintenance mode. It hasn't received new features in a decade (other than the port to .NET Core, if that counts). The Windows team has staffed it with a skeleton crew (a manager and 2 devs last I checked). They don't have bandwidth to review most community PRs, and even the .NET team doesn't get responses to issues: https://github.com/dotnet/wpf/issues/3811
idk, I hope I'm wrong but they have been promising improvements for a while and I'll believe it when I see it.
Ooof, yeah, I should have looked at the commit history. It does look like a skeleton crew and all the knowledge of WPF is in another team now. What a shame. At least WPF is stable for what it is though.