Family guy isn't cancelled, there just haven't been any episodes recently. Because they were on season 9, and the last episode to air on tv for season 9 was it's a trap may 22, 2011. And that was the finale LAST episode of season 9. So season 9 has official ended. But, Season 10 will be starting in the summer/fall 2011,
and they have already given a preview of what season 10 is going to be about here's the what they said (quote)
"Next season, Peter befriends Ryan Reynolds (guest-voicing as himself), the Griffins struggle to stay grounded after winning the lottery, Meg falls for an Amish boy and Stewie gets behind the wheel to take the family car for a spin. Then, on Meg’s 18th birthday, Quagmire moves in for the kill, and Peter tries to put an end to the relationship. Finally, Brian and Stewie travel back in time to the very first episode of the series."
and here is what else they said:
"In addition to the regular cast, FAMILY GUY has featured guest voice appearances by a long list of notables, including Cheryl Tiegs, Drew Barrymore, Chevy Chase, Dan Aykroyd, Anne Hathaway, Robert Downey Jr., Rob Lowe, Hugh Hefner, Will Ferrell, Jay Leno, Jimmy Kimmel, Kiefer Sutherland, James Woods, New England Patriots quarterback Tom Brady and the legendary rock group KISS. Guest voices for the upcoming season include Cate Blanchett, Rainn Wilson, John Ashcroft, Rush Limbaugh, Sean Hannity, Drew Carey and Bill Maher."
That right there was released by FOX for the upcoming fam guy season 10, which is PROOF, and one more PROOF for you Family Guy and The Cleveland Show were both re-newed until 2012, giving them another 1 or 2 seasons, until they are renewed again