Still not convinced

[Geoff D]

But the irony is that by the time Dolby Vision compatible players & software arrive then the SDR mapping issue may well have been cracked.

Dolby themselves are fully aware of this and have their own Content Mapping Unit (CMU) which generates the requisite metadata from whichever source, so even though the UHD Blu implementation of DV doesn't use an SDR layer at all we should still get a far more 'authentic' SDR grade from a Dolby Vision disc.

This is providing that the stars align re: dynamic metadata which hopefully the DV players will be able to read directly and output the internally-remapped grade accordingly, avoiding the small wrinkle that you might need a new HDR TV with HDMI 2.1 (or whatever it gets revised to) in order to view the true SDR downgrade