Zachary Levi recently talked a little bit about the problems Lauren Cohan’s character will cause on Chuck.
“We’re going to get some super secret weapon component,” he said. “Then [Vivian] shows up unexpectedly and all hell breaks loose and Bob’s your uncle.”
As for whether or not there will be a fifth season? Yvonne Strahovski said that she thought that the chances were ‘pretty good,’ while co-star Adam Baldwin said that he felt ‘cautiously optimistic.’
Source: E! Online