When exactly will FX's hit series It's Always Sunny in Philadelphia end? Well, as the show approaches its season 14 premiere, a few of the key cast members — Danny DeVito, Charlie Day, and Rob McElhenney — are ready to share their feelings about the matter. DeVito, Day, and McElhenney joined fellow It's Always Sunny co-stars Glenn Howerton and Kaitlin Olson in an extensive, recent interview with Entertainment Weekly about the show going into its epic 14th season, making it one of the longest-running television shows in the history of the medium. With a season 15 renewal …