Still very much in development (has the schedule slipped? - I thought it was due earlier this year.); but there are some notable improvements to engraving, listed in this document here: https://musescore.org/en/node/330793 (Document is actually dated March, but I don't think we've discussed it here?)
The improvements are all welcome, though the existing behaviour in v3 is often quite surprising, such as:
"Previously, individual staves of each system could start at different positions, depending on the length of each instrument label"
"The endpoints of ties will now automatically clear dots, flags, stems, noteheads and stave lines"
There are also improvements to playback -- VST3 support, and functional gradual tempo changes.
The release probably won't be until next year, and MuseScore is still playing catch-up -- but of course it stands out for one thing: the price. Maybe next year or maybe the one after: if you can knock out a reasonably attractive score, with well-adjusted beams and well-positioned slurs, with minimal effort, for free, then the commercial players need to bring considerably more than that to the table to justify any price tag. I don't think it's partisan to say that very few of them** are doing that.
** not forgetting that there are seemingly countless numbers of notation apps, all vying for market share.
