Here's the official link to Canon USA in regards to the rebates.
It appears Canon will be extending and increasing some rebates through to March 3, 2012.
A few notable lenses have been removed for the extension. The 17 f/4L & 24 f/3.5L II tilt shift lenses, as well as the 20mm f/2.8.
Lens & Speedlite Rebates at B&H (Extension not posted yet)
Source: [POTN] (I can't link, you need an account to view) & Bernie