As of this point in time MPI is only releasing DSTB DVD sets to their DSDVD Club members. They are not available to the general public, and probably won't be for about a year--that's speculation among many 'round these parts anyway. If someone has some concrete stuff to say, I haven't heard it or I forgot about it.
As for how they'll be released, it probably won't be in ony huge set that has all the episodes. They'll do it like they are now, releasing 6 sets of about 40 episodes each (I'm not sure how many episodes will be on the last set), just like the releases with the DS episodes that have Barnabas in them.
Hope this helps.