But if we are just wishful thinking here, I wish for a 70-200/4 IS or a 200/2.8 IS long before I wish for an additional wide zoom.
This is an interesting discussion on its own.
I think Canon doesn't make a 70-200/4L IS because it would be only a stop off the 70-200/2.8L IS (including IS "stops"), and thus they feel it would eat too much market share.
As for a 200/2.8, I wouldn't bother, probably. IS = more elements = less image quality, in the typical case. True, they've somehow pulled off *not* doing that in the case of lenses like the 300/2.8L IS, but the 200/2.8 is a sub-$700 lens, so either the price or the image quality would suffer, I'd think. I didn't wait to see if a 135/2L IS came out, because I figured nothing was going to appear at the same price/image quality point any time soon.