Well it seems as if it is official, 24 will not be returning until 2009. It has been mentioned by two different individuals who are close the project that it will not be returning until 2009 even though they already have 8 episodes already shot. To add to that news, executive producer Joel Surnow will be leaving 24 effective immediately. The links bellow will get you to the appropriate articles concerning the show.
24 Executive Producer Joel Surnow Leaving Show
24 Creator Surnow Clocks Out