In an interview with Kerrang, Green Day's producer, Rob Cavallo, let it slip that the band is currently demoing new material. Cavallo stated:

"I recently heard five new songs that Billie has written and demoed. Let me tell you, they were just fantastic. He is absolutely at the top of his game. Fans can be sure that when they do return, the music will be amazing."

You can read the interview here.