He said it would be the last time they perform for a very long time.
But you shouldn't take Billie completely at his word; I'm sure they'll be back pretty soon. Maybe not in the next few years, but trust me, they're not going away for very long. I mean, look at the last major rock star who said something like that at a concert: Dave Grohl. He said on stage at Pinkpop that the Foo Fighters would be taking some long-ass break, but then came his Sound City movie which the band eventually became involved with, and news broke recently that they're already working on a new record/project. The Foos aren't a band who like to slow down, and neither is Green Day. They both thrive on a strong, constant work ethic. Sure, they'll take a couple years off, slow down just a little bit, but Billie has too many songs in his head to stay away from the studio or the stage for very long.
With that said, if they do tour next year, I really don't care what theme they choose, although I would prefer either a Dookie tour or a Pop Disaster 2.0 than an AI tour.