Rumours are, as always, all over the place. Heck the 24-70mm MII rumour has only just come true and they were mostly wrong about that (no IS) and that one has been "rumoured" for years now.
For the 5DMIII the only semi-certain fact is that one was spotted with a 200-400mm in Africa. At least an unidentified camera was seen being used out there with the lens. It's supposed that, from looking at the cameras design/outer body shape that the 5DMIII (if that is the camera that was seen) will have an upgraded AF system - with many hoping/wishing/thinking it will be the same/similar AF that the 7D sports currently.
Other rumours are all up in the air and, honestly, you might as well pic MP values out of a hat. Some say more, some say the same some even say less - the only ones who know are canon and they are not letting on.