Don't forget, a lot of the technologies which have made the D800E competitive with some MF bodies would also benefit MF if they were transferred to MF digital backs. A full-frame 645 (56x42mm) CMOS sensor could very well have 15-16 stops of DR (using DXOMark's reference ranges), high ISO capability, 100-120MP and fully-functional live view. Same goes with a panoramic 24x72mm CMOS sensor.
But, with the D800E being the new benchmark, and future 35mm-format sensors improving on it, these benefits will likely only be relevant to 1% of photographers, and affordable to just 1% of these. MF manufacturers would do well to concentrate on the $10k-$15k end of the market, rather than $40k digital backs, and provide a greater variety of lenses, particularly at the wider end. After all, if Hartblei can stick a Canon TS-E 17L onto a MF digital back, while still retaining tilt/shift capabilities, then so can Zeiss, Schneider or Rodenstock. At the moment, you can shoot wider on a single 35mm frame than on a single MF frame, which is a big disincentive to go MF. But, with a proliferation of $10-$15k CMOS bodies and better UWA capability, a lot of people who would otherwise have bought a 35mm system would be tempted to go for MF instead. These are people who shoot primarily at the UWA-to-medium-telephoto range, who don't shoot action and need the flexibility of camera and lens movements - something that MF does much better than 35mm formats.