It looks like Canon extended the rebates again until March 31. I see the following at Canon Direct lens pages. Seriously, they should just reduce the list price and move on
Offer valid February 5, 2012 12:01 a.m. ET through March 31, 2012 11:59 p.m. ET, or while supplies last, whichever is earlier. Offer valid in U.S.A. only, and void where prohibited, taxed or restricted. Limit of ten of any one item per order. Dealers, distributors and other resellers are not eligible for this offer. Order will be shipped to a street address in the 50 United States or the District of Columbia only. Offer subject to Canon Online Store Terms of Sale.