Well, NOW there's a rumor about a new 10-22mm.
Well, there's a reason this site isn't called canonfacts.com, rumours have to start somewhere
Assuming the info was correct, and it is about an EF 10-22 replacement, i wouldn't think there'd be that much incentive in sheer volume to update it ... but if you look at the sales numbers of the Tamrons, Sigmas, Tokinas, they must add up to enough of a reason to update the 10-22. Some have better IQ in parts, some have a wider range (down to 8mm), the Tokinas have fixed f/4 and f/2.8 apertures. I still can't decide where the sweet-spot in all of them lies so haven't bought one yet.
But maybe the original 'rumour' could have just been mis-interpretation of the 8-15 f/4 fisheye (De-Fisheye it and it might beat the 10-22, anyone tried it yet?) or the 'rumoured' Full-Frame 12-24 (hey, if they can zoom down to 12mm on full frame, they should be able to zoom to 8mm on EF-S, even sigma can do that, do you want sigma to beat you, eh, canon?).
Still, i'm more excited about the EF-S 11mm f/2 prime patent, but not holding my breath to hold one in my hands...