Here's my idea:
The main set ends with 'One'
Crowd cheers for five minutes
The band comes back out, Bono says:
"Thanks, thanks for givin' us a great life...I know I say that all the time, but, but we mean it from the bottom of our hearts you made us what we are and, and we can't really put into words what you've meant to us, over the years, putting up with all our BS, sticking with us, givin' us the chance keep making the music we wanted to make and always embracing it the way you have...we can't put it into words but we can sure as hell try to put it into music, so, this is Acrobat"...
Acrobat
Edge and Adam switch instruments, while Larry keeps the beat going, and Bono says
"in case we didn't get it right with that, try this...for the last time, sing this with me, this is 40"
40
At this point, with the crowd still chanting 'how long', Bono says that Larry would like to address the crowd
Larry: Thanks a lot, guys...when I posted that note at Mount Temple...I couldn't, in my wildest dreams, imagine that it would be the beginning of all this...I never imagined I'd dress in drag for a music video...or get to swim with an actress playing a mermaid for a music video...I never imagined I'd sing dirty old town in front of god knows how many people...on the other hand, I never in my wildest dreams imagined that Bono could take his stupid mullet and make a fashion trend out of it, so what did I know. What I did imagine, though, was that if I ever did get to be in a band, that we'd have decent fans. Seems I was one-upped in that big-time, 'cause you guys are the greatest f**king fans in the world, so...I just wanted to say thank you for all of that. Goodnight.
The rest of the band waves and says goodnight as they walk off the stage, and the crowd keeps chanting 'how long' while similtaniously cheering, and for ten minutes the houselights remain off...finally, the band re-emerges, and without saying a thing, they gently drift into the first, last, and only ever performance of
Always Forever Now(from Passengers)
at the song's conclusion, after moaning the words 'always forver now' for the last time, instead of saying 'goodnight', Bono says 'goodbye'
The band walks off the stage, houselights turn on, end of show.
For those that lack understanding where symbolism is concerned, they play 'always forever now' as if to imply that their music will be with the fans forever.