I used to hate Kenny. But by the end of this series, I grew to love the stupid guy. And I will fight to the end that he deserves Unknown status on the Wiki page.
People have already said it, but just to clarify: it has happened before in TWD that people who were assumed dead (but whose death's were not seen) ended up surviving: Tyreese, Andrew (in the show).... Lee manages to fight his way through that entire herd. Rick has managed to survive without a fucking hand. TWD is realistic in that they kill people off that have been around for a while. TWD is also unrealistic in that they allow people who should have died a long time ago to stick around.
Also, if you get the Ben scenario: if you ask Christa and Omid to keep an eye out, Omid clearly states he can not see anything. Then when Lee returns, Christa asks what happened and if he actually saw them die. The end of the game uses the word "lost" and not dead. Kenny is probably dead, but the thing is WE DO NOT KNOW. We see Kenny run and hear some weird noises... how do we know the walkers didn't stop to eat Ben? How do we know those noises aren't them eating Ben?
Kenny may have seemed like he was giving up, but how many people when faced with death decide that maybe they aren't ready to give up? Especially when they just gave a speech saying how terrible suicide is?
I paused it here and tried to brighten the picture.... does it look like the walkers are swarmed around anything? It looks as if they are just passing through. I kept pausing and did not see any sewer, but there is always the possibility that Kenny ran for it... and just like Lee, maybe he got enough blood on him to get through.
The Christa version is even more likely for Kenny to have run out of there.