"Also in development is a focal length reducer for EF lenses, this will be announced with the 20mp EOS M camera"
That is something you hear about more in astronomy. But a 0.8 focal reducer that would turn your 10-22 3.5-4.5 into, say, a 8-18 2.8 - 3.6 would be interesting. A Meade or Celestron focal reducer costs in the neighborhood of $100. Count on the Canon being $300, maybe. Because it is Canon, and because it has the EOS electronic connections.
Let's see -- a .8 reducer would make the 85 1.8 a 68 1.4. But the efl would still be a bit over 100mm because of the crop factor. This sounds intriguing, but will probably not be inexpensive.
A reducer factor of 0.63 would restore EF lenses to their full frame optical values. (0.63 = 1/1.6). I wonder if that's it....
I would expect a factor of .707 (sqrt(2)/2) mainly because it would be an even 1 stop difference, whereas a factor of .63 comes out to a very odd 5/4ths stops.
85/1.8 would become a 60/1.3
24-70/2.8 would become 17-50/2
70-200/4 would become 50-140/2.8
I think that would be enough to make focal lengths that are only so-so on crop (24-anything) quite attractive.
...and the 60/1.3 would become a 85/1.8 equivalent,
the 17-50/2 would become a 24-70/2.8 equivalent,
the 50-140/2.8 would become a 70-200/4 equivalent,
on a crop body.
The 85/1.8 converted to 60/1.3 would behave like a 96/1.3 instead of a 128/1.8 if unconverted
The 24-70/2.8 converted to 17-50/2 would behave like a 27-80/2 instead of a 38-112/2.8 if unconverted
And the 70-200/4 converted to 50-140/2.8 would behave like a 80-224/2.8 instead of a 112-320/4 if unconverted
Obviously all these numbers are with a .707 conversion factor, which is just my guess, and a 1.6 crop factor.
Also , when I say "behave", I'm talking about FOV and exposure. DOF/bokeh/etc., not included.