People don't understand humor.
Nobody has ever understood humor. What people find funny is so subjective that it's always odd to me when someone states as a fact that something is or isn't humorous. I realize people have
always done that despite it being one of the least possible things to argue logically, but still.
More on topic, I saw Anchorman a long time ago and don't quite recall how it ended, but I don't remember it being a particularly open or sequel-needing situation. Hopefully for the movie's sake it's not too forced.