I say yes to Library Manager addition. I'd like to see Library Manager become a comprehensive catalog of all Arduino libraries. Even though it already has >1400 libraries I still end up doing a Google search to discover libraries because there are a lot still not in the Library Manager index. I also really like the automatic notifications of new releases of my installed libraries that are in the index.
That said, I haven't added my libraries to Library Manager. I probably should do it, but I think I'm probably about the only person using them (and for good reason). My personal feeling is that, as long as the library author has made a reasonable effort to write working code and provide sufficient documentation, every library should be added to the index. I'm not sure whether that sentiment is shared by the rest of the Arduino community or if there is some additional standard of general usefulness that should be expected from libraries added to the index. Certainly that standard would need to be self-imposed since there is no way for the Arduino team to vet the quality of libraries that are submitted for addition beyond the automated check of the metadata and folder structure. Maybe the solution would be to offer an interface that shows usage statistics, ratings, and reviews of a library.