It's Always Sunny in Philadelphia recently wrapped up Season 8, with Season 9 set to debut next fall. Since most cable shows rarely make it past eight seasons, this is a milestone in and of itself. FX Network president John Landgraf revealed today that It's Always Sunny in Philadelphia will likely be renewed for a 10th season.
"There is a high likelihood for a 10th season. Whether it goes beyond that depends on whether the people who created the show want to go and whether the audience still wants to watch. But there will definitely be one more year, probably two."
John Landgraf also called the series one of the "four cornerstones" of the network, along with The Shield, Nip/Tuck, and Rescue Me. It's Always Sunny in Philadelphia, created by Glenn Howerton, Rob McElhenney, and Charlie Day, is the last of these "cornerstones" to still remain on the air.