I suspect BandLab are trying to balance getting feedback for existing bugs, whilst trying to ensure their existing customer base doesn't migrate to another DAW.
IMO, CbB is the most stable incarnation of Sonar to date. Having this "closed" (by which I mean no new members) and relatively experienced community report bugs and suggest improvements allows BandLab to focus on getting Cakewalk rock solid, and finally put to rest the buggy reputation Sonar has had on forums elsewhere.
By the time a new forum is ready, our accounts are migrated over, the new store is ready etc, Cakewalk can get the exposure it deserves without fear of the odd bug letting it down.