and it wouldn't surprise me if D800 outshines it in both high iso (likely, esp with lower MP) and DR (as usual).
Aimed at studio work (or macro) with controlled lighting, dr and iso wouldn't matter much, you'd just want high mp for enormous high gloss prints.
46.1 mp eh? I imagine that would allow Canon show optical superiority of its lenses in comparison to the competition ( and hopefully not vice cersa )...
Most manufacturers can/could produce very sharp lenses for a lot of $$$ - Canon's main advantage is the af system and its integration with the (newest) camera bodies. But if Canon produces all future L lenses for 46mp+ they'll be very expensive, too, even if you use "just" 20mp. The 24-70ii must just have been a taste.
If its a 5Dx for 4099$. I'm so buying one.
Most people who got a 5d3 for $3500 will happily trade it in for a 5dx for $4500 - At least that's what I hope, because then the rest of us can get the used, cheaper 5d3 bodies :->