Extra interviewed both Yvonne Strahovski and Mary Lynn Rajskub and they mentioned the numerous different endings.
Does it leave itself open to continuing, or is this the [series] finale?
Rajskub: I think it was originally conceived as a completion of the whole thing. But now… questionable.
Strahovski: There were quite a few different endings that I think they were playing around with.
Rajskub: Quite a few different endings.
Strahovski: So up until the minute of shooting certain scenes, we were still rewriting; on set even. Rewriting, rewriting, changing things.
What’s it like working with Kiefer Sutherland?
Strahovski: He puts a lot into it, not just as an actor but a producer as well.
Rajskub: He’s very gentle and generous and fun loving. So he’s got Jack Bauer work mode [and chill mode].