It hasn’t been mentioned on this forum, but on the VI forum, Arne Wallander has said:
NotePerformer 4 won’t be released before the end of the year, but I dare to say it will be released in Q1 2023. The core engine is already in a fully functional state, but there’s still NotePerformer 3 functionality left to port to our NotePerformer 4 platform, and some polishing to do. I know it’s been four years since NotePerformer 3 was released, but we’re going to introduce some disruptive notation program technology. I think everyone on this forum will consider it worth the wait.
We will have a free upgrade path to NotePerformer 4 with no cost penalty, so there’s no reason to hold off on your purchase.
For the record, we don’t plan to charge for updates to our core software, but we may charge for supplementary content, which is optional for the user.