Marvel Cinematic Universe
When someone says "it's all part of the plan," that's a sign that it is most probably not part of the plan. In fact, it's unlikely that there ever was as plan to begin with.
That's not the case with Avengers: Age of Ultron, though. This movie plays a very specific role in a much larger set of production decisions. Along with films like Iron Man 3, Thor: The Dark World, and Captain America: The Winter Soldier, this film is part of "Phase Two" of the Marvel Cinematic Universe (MCU). In all, three phases of films are planned, giving Marvel Studios and its parent corporation, Walt Disney, plenty of opportunities to tell superhero tales—both as individual stories that focus on one or two heroes by themselves, and as team-based stories, like the Avengers movies. In what company executives would undoubtedly call a "win-win," this approach also allows Marvel and Disney to squeeze maximum buckage out of their many franchise stars. Now isn't that special?
It really is, when you think about it. There's nothing quite like the scope and complexity of the MCU when it comes to movie making. (You could argue, in fact, that was Disney is looking to do with the Star Wars franchise is really just following the model established by MCU.) We're talking north of twenty movies, with characters whose arcs take them in and out of varying story lines, and with each interaction rippling through the plotlines of the other films. No wonder Joss Whedon had to take a break after writing and directing the first two Avengers movies. (For more on him, check out "Screenwriters.")
Even as he steps down, however, the franchise steams ahead, unleashing at least ten movies with the launch of Phase Three. All of this is starting to sound like an Avengers movie itself, which is probably no accident. From a production standpoint, Age of Ultron had to keep the box office momentum going from the first Avengers, advance the characters and plotline toward the Infinity War movies, and sustain audiences' interest along the way. Sound like an impossible task? Luckily for us, the brains at Marvel and Disney were up to the task. We wonder if they were capes, too.