Last month, we were in a funk, because at Comic-Con executive producer Al Jean said they were writing a 2011 Christmas episode featuring Homer and Marge as grandparents, which would apparently confirm a 23rd season.
But in a recent interview, Jean jokingly suggests otherwise:
My math could be incorrect, but I believe your 500th episode will be airing this season. Are there plans for an extended special to celebrate this milestone?
Al Jean: I’m afraid your math is incorrect. Our current record schedule will take us to episode 493, so if Fox wants 500, then I’m afraid they will have to pick up season 23, hint, hint.
NOW I DON’T KNOW WHAT TO BELIEVE 
[MovieWeb.com]