They haven't, and I wouldn't expect it any time soon. I doubt they will ever allow post 6/20 weeks to enroll for the same enrollment fee they offer today.
My guess is that they will allow some type of re-qualification in the future where if you buy x,xxx DC points, you can enroll your post 6/20 week(s). I think their best move would be to say if you buy x,xxx DC points, you can convert your legacy weeks to DC trust points. This will give them added control over inventory. Not that I want them to do that, but it would make the most sense from MVCI's standpoint.