There's a roadmap.md on github showing MS's intentions for WPF -- first and foremost, porting to .Net Core. So there is, at least, active (and I'd say significant) development. But...

Not trying to sound facetious, but does WPF need any other significant work? It's a UI framework for Windows desktop apps (narrow and specific scope), it's stable and "just works", it's well-documented, it's officially supported, etc. Does there need to be anything else, or are we looking at it from the POV of more "modern" UI frameworks, where no active churn == languishing on the wayside?