BSI is not all good, there are some challenges with it too related to manufacturing, electrical crosstalk, pixel non-uniformity etc. The A7r-II (BSI) seems to have (very) slightly worse DR than the older A7r. I think the main advantage of BSI so far is good high ISO, not better DR at base ISO.
I don't think this new sensor is a BSI sensor, but it's just a pure guess. We'll find out at some point. I don't think it's actual 15 stops either (DxOMark per pixel definition, but indeed downsampled 8MP definition they will probably do it), something also time will tell.
It's surely 100 MP and 645 fullframe and all the usual CMOS advantages though, and I think it's so revolutionary that I would not be surprised if the IQ3 is the last range with CCD sensors in them, because who's going to want to buy a new 80MP CCD now with this new king of the hill?