I wonder if this is in response to the 40mm by Panasonic?
Anyway its exactly what I want and I'll prob swap my 35mm f2 for it.
As to everyone wondering why this makes sense, I don't want to buy another small camera with rubbish battery life and lower image quality, with small viewfinder.
This allows somebody like me to leave the 24-70L at home for studio and still use the 5D for fun, without the extra weight.
When they bring out a lighter full frame DSLR to go with it, I will bite, so long as its still as good as the old 5D and comes with video and a built-in flash.
Its a masterstroke as far as I'm concerned and will make Canon a viable alternative for those considering aesthetics, viewfinders, and weight as well as quality, such as Leica and Fuji.