1. No one knows when version 4 will be out. I expect, not for some time, and we'll see a version 3.5 first. Then maybe version 4 at least one or more years later.
2. You don't say what comprehensive MIDI editing tools are needed. Do you have specific tools in mind? If so, what are they? How do they work? What are the benefits over current state? There's certainly a few MIDI improvements I'd like to see made, but there are already open, and specific feature requests for those that can be voted on. If you have specific things you think Studio One is missing, you should edit your original post and elaborate. Don't forget to search the forum and see if there are already open requests, and if so, vote on them.