User blog comment:Dragonknight86/Phineas and Ferb on Hiatus after Season 4 ends/@comment-3466679-20140329135900

Dan posted on twitter that they were songwritting for PF. I remember that when they started songwritting "evil for extra credit" was 1 year prior to the episode (the same happened with "Doofenshmirtz Swanky New Evil Lair"). so if they are songwritting now, that episode should release in march of 2015. And if the song had been for an episode like the last one. They would have posted it.