I hate to see it end, but there are only so many plots that can be created around nuclear bombs/rods and lethal viruses that only Jack can find.
I do think we will see 24 the movie though.
from TVGuide.com article:
Despite reports that NBC was considering picking up the action series if it were canceled, [Executive Producer, Howard] Gordon told The Hollywood Reporter that the writers could not come up with a story line for the ninth season.
They ran out of ideas. Thus, the Hands-and-her-former-life story line.