Among other rumors (which I find too vague to mention here) on the 5D mk3 canonrumors recently wrote:
February 2012 would be the earliest for an announcement that will address the 5D line.

If we picture February 2012 as an announcement date for the mk3 then May/June would be realistic release dates as Canon usually announces several months prior to release.

Considering that 3 years have passed the development and improvement of Canon video dslrs has gone very very slow.
The 5D mark II still almost matches and in some aspects exceeds the video capabilities of all the other (later) Canon hdslr cameras.
Usually we see a different stills camera come out with just the same video functionality in it and all the major problems we don’t like so much. Video still seems to be treated as a side effect to these dslrs.

Well, somehow it’s legit, after all these are still cameras that come out of the stills factories of Canon, so maybe one could say: “Why should they care, they develop for photographers.”.

We seem to finally have come to a point in time where our (dslr filmmakers) dependency on the Canon stills factories for new hdslrs is coming to an end.

Other companies like Sony, Panasonic and Nikon have and are developing great alternatives.

Take the Sony FS100 for example, one of the more affordable video cameras that has a large sensor and interchangeable lenses and delivers great images with all the video advantages.

Or the Panasonic GH2, that has recently been hacked (for higher data rate), has virtually no moire, less rolling shutter and even delivers a sharper picture than Canon dslrs.

And Nikon is up for a major announcement in late August, talking about development of a new generation of digital cameras.

I dare to claim that Canon has given up it’s advances in this field and unless they release that affordable cmos video camera quickly the customers will soon have picked up the products that quickly come in by other manufacturers.

As a closing here’s an excerpt from an article by Philip Bloom on a similar topic:(…) we are still on generation ONE of Canon DSLRs that shoot video. We still have the hideous line skipping, the bad rolling shutter, the aliasing and moire from hell. We still have no headphone jack, no proper control over audio…the list goes on. But we put up with them, because we love the image. But it really is time for generation 2. Canon simply needs to bring out a 5DmkII replacement soon. There is competition now, and it’s not from other stills manufacturers. (…)