Although the Renew/Cancel index lists Chuck as safe and likely to be renewed, the index has never encountered either an NBC that is performing as poorly as NBC is this year, or an NBC that is cutting five hours out of its prime-time lineup next year to make room for Jay Leno.
While I won't be terribly surprised if NBC renews Chuck, I won't be surprised if they don't either. Chuck's performance relative to NBC's average season-to-date 18-49 viewing (minus the) is OK, in fact it's almost performing exactly at the average. However, NBC's average stinks. Still, normally shows that perform average are not canceled by networks. But normally, networks don't clear five hours of the prime-time schedules for Jay Leno. Since Chuck's numbers aren't great (or even good, honestly) in the absolute, I don't think its fate is sealed just because of its performance in the index.
We probably won't know anything before NBC announces its lineups in early May and are just going to have to ride it out until then. While hand-wringing won't change the show's fate any, it at least gives fans something to do between now and early May! And the fans don't have to sit idle because the results for tonight's episode which we will report tomorrow (Tuesday) morning will be interesting at least for me.
The last time Chuck aired two weeks ago, it aired against a full line-up of competition, including the premiere of (one of the best premieres it had in years). Tonight though, House is a repeat. Two weeks ago when it wasn't Chuck averaged 5.7 million viewers and a 2.0 with adults 18-49. Without a new House, I am looking for Chuck to improve by at least 10% -- meaning it will go back to having more than 6 million viewers, and more importantly at least a 2.2 rating with adults 18-49.
If it does increase by 10%, I don't know that it will really mean anything positive to its survival. But if it doesn't increase by at least 10%, I would view that as a significant negative and think it likely the folks at NBC would too.
While I am a huge fan of Chuck, there are some things I don't necessarily share in common with the fandom. For one, if NBC winds up canceling Chuck because it thinks it's a marginal performer, I won't be able to fault NBC for such logic. I won't be mad or upset at NBC, and I will be happy that they at least aired around 35 episodes of a show I really liked. That's how I feel about most shows. Life (also on NBC) will surely be cancelled, and Life on Mars (ABC) already has been canceled and its series finale will be on April 1.
I don't feel like the networks are treating me personally badly by not renewing shows that don't have great ratings, and the knowledge that those two shows are done doesn't really do anything to take away my enjoyment of them, and if NBC winds up not renewing Chuck, I will feel exactly the same way. But I understand I do not in any way speak for all of the fans with that particular viewpoint. Indeed, I may even be in the minority.