I think what Sony have done is brilliant. In Australia, Sony are offering a free metabones adapter by redemption. I have too many lenses to consider a switch to Nikon and there is no way a Nikon mount could ever take a Canon lens, but with the Sony I can get an A7R and use my existing lenses with it. Of course the autofocus is slow, so for certain things I would keep my 5D2 and 24-105 combo at least initially.
If the E mount 24-70 F4 lens is a good one (and you would expect it will be) when funds allow I would get that as a walkaround, with my other lenses to be used for slow landscape/tripod work as mentioned by someone else above. The 5D2 would then be sold.
They have given me an option that doesn't involve thousands of dollars to change systems straight away. I can keep a foot in either camp and simply buy the most appropriate body at the time. If Sony keep producing brilliant Zeiss lenses for the system AND stay ahead in the body/sensor game, then eventually I'll end up with more native lenses. And just like that, Sony have converted me.
I'm not sure that there would be many people who would be looking at a $2300 36 megapixel camera as their first camera purchase. The target market are going to be enthusiasts and professionals who would already be heavily invested in either the Canon or Nikon systems. Therefore this is a smart move by Sony, who realised they would have to do something different to get CaNikon users to switch.
When you think about it, an A7R with a 24-70 will cost only fractionally more than a D800E body only and take pretty much any lens - sweet!