This is an artical I found:

It’s been more than a month since NBC aired a new episode of Chuck, and sadly for fans of the hit comedy series, the network has yet to announce when the remaining episodes are set to air. On the bright side, however, plot details regarding the upcoming installments have hit the web, which gives way to some much needed spoilery for willing viewers.

Warning: spoilers ahead!!!

According to SpoilerFIX, an episode entitled "Chuck vs. The Marlin" will introduce two new people who are trying to take the show's geeky hero (Zachary Levi). One of the two happens to be a beautiful and young enemy agent that works in the Pita Palace next to the Buy More. The other is a handsome CIA agent who is posing as a police detective. The man claims to be working undercover as he investigates a theft at the Buy More and says that he wants to take Chuck into custody.

End of Spoiler!!!

SpoilerFIX says that “Chuck vs. The Marlin” is the 12th and last episode to be completed before the writers’ strike began, but TV Guide’s Michael Aussielo is reporting that there are actually two more left to air, since the show is expected to complete 13 episodes all in all.

Various sites are claiming that the other upcoming Chuck episode is called “Chuck vs. The Undercover Lover,” but because the network has yet to announce the air dates, it is unclear which of the two new episodes will air first.
After all 13 episodes have been aired, fans will have to go through another waiting period before they can view the nine episodes which NBC picked up late last year.

“We have a back nine, [but] we don’t know when we’re going to shoot,” Levi told Entertaiment Weekly last month. “It wouldn’t surprise me if the network says [those] nine episodes will be the beginning of the second season.”