In a recent interview, Joss Whedon explains that The Godfather Part 2 is his 'guiding star' for Avengers: Age of Ultron. He also explains that Captain America: The Winter Solider will affect the events of his Avengers sequel, but also says that you wouldn't have to see Captain America to get what's going on in the Avengers storyline. Here's what he had to say to AlloCiné.fr,
"The events of Captain America [The Winter Soldier] will definitely affect the world of Avengers 2. But at the end of the day, I have to make my movie assuming that people will only have seen the first one, or possibly not even seen the first one. I can't assume that everybody went to see Thor [The Dark World], Captain America, and Iron Man 3 in-between. I have to go from one movie to the next and be true to what's happened [in the previous movies], but not be slavish to it. [...] The model I'm always trying to build from, or my guiding star, is The Godfather: Part II where a ton has happened in-between and it's a very different movie [from Part I], but you don't need any information. It's there in the film about what's happened since, what's different, and why is this a different film; why is it a different kind of structure, and why is it darker. It's all there, you're in the vernacular of the first movie and you're just ready to pick up in this new place, and hopefully that's what will happen with my movie. Obviously I'm talking about one of the greatest films ever made (The Godfather: Part II)... I hope mine will be good, but that is my guiding star."
The Godfather Part 2 is one of my favorite movies of all time, and the fact that that Whedon is using it as his inspiration for his next film is encouraging. I'm sure Age of Ultron is going to turn out incredibly well and will make fans incredibly happy. It's set to be released on May 1st, 2014!