Here is the end-credit scene that I think would be absolutely aweome!
After the Avengers have defeated Ultron in Sokovia, they rebuild in upstate New York to train the New Avengers. Meanwhile, a nuclear silo is testing nuclear weapons. We pan through the whole building while they are initiating a countdown on the missile when we reach the main computer of the site. As they reach 10 seconds on the missile, we here the ominous words, "Ultron Program uploaded." Cut to black. End of film.
Well that is my dream end-credit scene. Let me know in the comments if you like or dislike it, agree or disagree with me. As always, bye bye, and see you next time.