I have almost been wondering this myself. I have been waiting for an alpha/beta of VL6 SOHO to come out so work on MMBD2 can begin. The main issue is that SOHO6 will be using KDE4 and many programs on the disc are kde programs. This means that I really need a working SOHO system with KDE4 to build the next disc. The original goal was to create the disc such that it does come out at the same time as the next SOHO, but I'm not sure how things will pan out.
Perhaps I should just begin with VL6 Standard and then rebuild/modify for SOHO, but things could get messy if I don't have the actual KDE libraries and such to build against that will be used in SOHO.