User blog comment:PF News/Tri-State Gazette, Issue 110/@comment-5037384-20140223144830/@comment-961279-20140305164012

It hasn't been announced yet, but they've likely been working on it for a few months. There's only about a half dozen episodes left in season 4 plus the Star Wars special and that will take us up to about August or September of this year. It takes 8-10 months to create an episode, so for a new season to be ready around then, January is the last month they could have started working on a new episode. If I remember right, Disney likes to show the last episode or two of a season close to the first few episodes of the new season, to keep momentum and interest going.