The actress told Collider that she did not expect the NBC comedy-drama to last for five years.
"I feel like we got a bit of a bonus season right now," she said. "We are having a lot more fun as a cast. We had fun initially to begin with, but I think everyone is letting loose and milking the moment. I think I can honestly say that this season has been the most fun with the cast."
She also suggested that there is "always a chance" that Chuck's final season could be extended beyond the commissioned 13 episodes.
"We have to stick with the notion... that the 13 will be it," she explained. "[But] if for some random reason they throw us back into the works and say, 'You know what? We need nine more' [then] we will do what we have always done every season and just pick it up where we left off."
Strahovski added that she still has no idea how Chuck will eventually end.
"I haven't asked [the writers] that question funnily enough," she revealed. "I don't know if I want to know."
Chuck returns on Friday, October 21 on NBC.
> Eric Lange, Beau Garrett land Chuck roles
Watch a clip from Chuck's fourth season finale below: