Some people seem to think so. I actually watched last night's episode, even though I normally don't watch South Park. I thought it was hillarious, and when they showed the "censored panels" at the end, I laughed my ass off. I personally think it was part of the joke, and I bet that Stone and Parker don't say a word, and keep people wondering, which only would serve to emphasize their point. And as one commentor on Volokh pointed out, Comedy Central has already shown a cartoon of Mohammed.

Update: Apparently Comedy Central did censor the image. So now Jesus crapping on a flag is OK, but Mohammed standing there innocuously is not. Makes you proud to be an American doesn't it?

Update II: More thoughts here.