This would actually be a good poll: Were they talking about the viewers getting older and more cynical, or themselves and their relationship with the show?
Just in case this hasn't been posted, here is the interview which states the show will go through 2013.
"the pair hurtles into the 15th season of South Park, part of a new pact with Comedy Central that keeps the show on the air through 2013 and is said to be even richer than their previous $75 million deal."
http://www.hollywoodreporter.com/news/why-south-parks-trey-parker-171189
Yeah, I had heard that as well. Maybe they were just venting frustrations in that episode, and next episode will pretend like it never happened? Or maybe the show will just take a dramatic turn in it's remaining years, Matt/Trey are capable of pulling anything really.