I think the next 1D Mark IV or V or whatever it will be, should stay as a 1.3x crop body. As previously mentioned, it's great for sport and action shooters to have that crop value IN the camera when you need it when shooting the action.
It should also have 10-12 fps, AND most importantly, have NO AF issues right from the start!! Get it right the FIRST time! As far as how many MPs it should have, I think somewhere in the 12-15 range, if not staying at 10 MP, would be good.
I think people tend to forget that not everyone can afford 2 or more camera bodies, and maybe someone wants a 1D series body for the high FPS rate, the 1.3x crop factor, and to use it in various types of photography, such as a nature photographer who covers animals, so the high fps would be useful in capturing a soaring bird, running animal etc, but also uses wide angle lenses to capture scenic images such as the Grand Canyon, Slot Canyons, Alaskan Glaciers etc, and even used with macro lenses.
And even if they do decide to purchase a second camera body, it would be so convenient to be able to have the same body so they wouldn't have to think twice about "Which body am I using?", and just keep shooting.
Now if Canon decided to make an EF 12-28mm f2.8L lens designed for 1.3x crop bodies, (a 15.6 - 36.4 mm FF equivalent) that might be something that 1D series body users might take a look at).
Just my 2 cents.