It has been confirmed... Day 8 is the final day in the 24 series. Here are the details from the Fox website.
In a joint decision made by 24’s star and executive producer Kiefer Sutherland, executive producer and showrunner Howard Gordon, Twentieth Century Fox Television, Imagine Entertainment and Fox Broadcasting Company, it was determined that the acclaimed series will end its remarkable eight-season run. Jack Bauer’s last day on FOX will conclude when the final two hours of “Day Eight” air Monday, May 24 (8:00-10:00 PM ET/PT). As the countdown to the series’ climactic conclusion races on, the final 11 hours will air uninterrupted Mondays (9:00-10:00 PM ET/PT) on FOX.