MF is not going to happen. And the Canon execs have been saying (in interviews after the launch of the 1D-X) that they can not say anything about products in development, but if the market asks for higher MP models, they can and will deliver that. So who knows what is in the pipeline, considering the competition (D800) too, with 27% more pixel resolution.
The image quality seems to be impressive, it has that dynamic feel I like about the 1D mk III files (materials look more real, colours appear more "deep" in the "normal" ISO settings sample files). Not sure yet about the higher ISO performance, as that ISO 6400 image has been ruined by some standard NR (Canon always does standard RAW conversions for their samples).
Only thing I am missing in this new 5D is no swivel LCD.
I agree with Klaus that it is a bit unfortunate that it is heavier at 950 grams, but I guess that is a price to pay for a more rugged build (Nikon D800 is even heavier). Although Pentax with its K5 shows it is possible to make a more compact, lighter camera.