Well maybe the release date hasn't been confirmed by Blizzard, but the BestBuy Canada website states they will have Diablo III (PC) in their warehouse on 02/28/2012. They are currently accepting pre-orders. If the retailer has a date, why doesn't Blizzard?
http://www.bestbuy.ca/en-CA/product/diablo-iii-pc/10152048.aspx?path=d2e594f9058378b16c4301e8a651f0f0en02