The rumors are true. "Chuck" will be back for a 13-episode 5th season, according to a reliable source connected to the show. 

I don't have any details beyond that right now - like whether NBC is holding out the possibility for a back-nine order at mid-season or if they anticipate these 13 being it for the order - but I wrote at length about the renewal rumors yesterday. Now, I'm just pleased. So celebrate with Chuck and Morgan humming their favorite entrance music, and we can go into Monday's episode knowing it's not the series finale.

UPDATE: Several other reports have said that NBC has made it clear that this will be the final season. The NBC upfront press call is Sunday afternoon, so I'll have a lot more info then.