It depends on whether the premium add-on was developed in-house or was licensed from a third party. In the latter case (including some features that aren't plugins), deals have to be renegotiated with outside companies.
CA-2A's file header says copyright Cakewalk, which leads me to believe it was developed in-house and there should be no barrier to selling it again. It's probably just a matter of setting priorities for the smaller development staff. It would be nuts for BandLab to own intellectual property and not try to earn revenue from it, so I expect most things will be available for purchase in time.
Other plugins that contain the same copyright information include Boost11, Dimension Pro, Rapture, DropZone, RXP, Session Drummer, Studio Instruments, TS-64 Transient Shaper, TL-64 Tube Leveler, VX-64 Vocal Strip, LP EQ, LP MB, Drum Replacer and PX-64 Percussion Strip. (These are just taken from my own current inventory; not sure which ones are already bundled with CbB.) I would expect all or most of these to be made available for separate purchase.