Well this is pretty much what I've been predicting all along.
I'm still calling it a 5D HD and believe it will be essentially the same body with a different sensor plopped in. I am surprised at the frame rate, I thought it would be lower. I wonder if they will give over some processing power to the frame rate by putting a more modest autofocus in this one. Not sure the people using this camera will need the 5DIII or 1DX autofocus. I've said it will be the same price as the 5DIII. Possibly it will come in slightly higher, but I don't see this as a 1-series body.
Yes, as 46mp, this looks like Canon will used the same sensor in this as they use in the next generation of 7D and probably 60D. With three years of experience with the 18mp (46 mp equivalent) it may mean Canon has decided to just improve upon what they already produce instead of trying for ever-more pixels. That's consistent with everything they've been doing the past year (1DX, 5DIII, 6D, T4i).
This bodes well for 7D users. Canon must deliver acceptable noise for the full frame body (Not sure I'm buying the 12,800 as clean, but if it is good at 6,400 or even 3,200 that would be a significant improvement) and since they'll likely use the same sensor in the 7DII at least, the APS-C version should perform identically.