I'd be a little disappointed if they were only able to add 3mp to the camera after 3 years.
Even though I don't think I want massive amounts of more mp, the following makes me think otherwise:
1) 2 days back I was casually shooting for a sporting practice and people were admiring the 70-300L, when someone asked me "How many Mp does your 5D have"... now before I could explain to this chap how mp's matter or not, the whole group went silent and was looking at me. This included a Guy with a 16mp PS... so it was kind of awkward explaining that I only had 12.7mps... cause he looked away unimpressed when I told him... err 12.7mp.. cause he did not want to listen how the 5D was better than the 16mp P&S.
2) I have recently taken a few pics of the full moon (moon HDR) and need to crop aggressively to get some detail since my 300mm on a FF can't do a whole lot in terms of zoom, and as cropping 12.7mp has it's limitations. Same with Macro... I think more mp's would be welcome as long as I can shoot at user selectable sRAWs / crops.