A recent patent publication shows Canon has been looking into adding image stabilization to a 24-70mm f/2.8 lens.  Given the recent announcement of the EF 24-70mm f/2.8L II USM lens (which still isn't available), however, this doesn't bode well for an IS version anytime soon.

Of course, there's a Tamron lens that fills this void though...

[via Photo Rumors]