Executive producer Al Jean told Digital Spy, “I don’t see an end in sight – ratings are really good.
“I think it’s going to go at least two more years, maybe four, maybe more.
“I’ve stopped trying to predict, because it always goes much further than anybody dreams.”
He also said there are ideas for a second film but there are no concrete plans.
Jean said a joke in the crossover episode in Family Guy was not to his liking.
The scene saw Stewie Griffin prank call bartender Moe, telling him his sister had been raped.
“I’d actually said to (co-creator) Jim Brooks that maybe we should ask them to change that, just because the word is so offensive.
“He said – and I respect this – that’s what they do and we don’t want to be the heavy hand that censors them. But personally I would’ve omitted it.”
The scene drew criticism in the US.
“Stewie makes the joke and everybody looks at him, like ‘That is not funny’ – but a lot of reports missed that second part of it,” he continued.
“The whole idea is that we don’t think that’s funny – we were saying, ‘We hate that joke’.”