All the answers we've been given are in post #1 of the sticky Hello thread. We've not been told anymore.
To summarise... Sonar will continue under an as yet undisclosed name, working title "The Daw Formerly Known As Sonar". All current owners of Sonar will be able to continue with the new version from BandLab as if nothing changed.
I'm fairly sure that the first release will not be much more of a re-branding exercise, both in name and look, but also to switch backend systems (authorisation, user accounts, etc.,) but you never know, there could be some surprises thrown in which would be nice.