There are a few extensions where trivial fixes would need be needed to make them compatible with recent Slicer versions, but the maintainers don’t respond to pull request and personal emails (see for example OpenCAD).
Should we move over these extensions to the Slicer GitHub organization?
Moving them to Slicer is a good idea I think.
We might also consider tagging an extension in the extension manager with a green/yellow/red label similar to (for example this) mediawiki extensions.
Or moving entries to a new Abandoned category, instead of their developer tagged category.
Interested parties could then adopt an extension.
Most extensions are licensed so that new maintainers can take them over with no restrictions. Definitely if they are valuable but unmaintained then any willing developer should feel free to chip in and fix them (hoping to draw back in the original contributors if possible).