I think Green Day needs to massively overhaul their sound with their next project. Do something different, something more contemporary, experiment. They don't really stand out all that much anymore. I mean at this point they're pretty much in a Post-Warning era-esque rut, so they might as well try to do something new since they have hardly any hype backing them anymore (at least in comparison to say, 5 years ago). Focus on making a tight, all-killer-no-filler record. No overarching narratives, no gimmicks, keep the album conceptually simple. Maybe try perfecting the sounds that they began to explore on Warning, but do it in a more modern way. I don't think they can really afford for their next album to just be another standard guitar, drums, bass record. People want something a little more dynamic.