Originally Posted by Terror Inc.
I would not mind seeing War Machine show up to help the team out, but I don't think he's necessary for the joining them. If they could explain away why he's not gonna join, i.e. the government wants/needs him somewhere else, I'd be fine with him showin up. But I'm already missin the Iron Man 2 armor, Stark is the one who's all sleek with fancy tech, War Machine needs to be a tank with a veritable warehouse of bad-ass weaponry.
The Iron Man 3 prequel comic already explained War Machine's absence from the first Avenger movie as an assignment against Ten Rings terrorists in Hong Kong. You can't conveniently have War Machine be "away on assignment" every time the Avengers get together to save the world.
War Machine is part of the comic-book Avengers, so he has every right to belong to the movie Avengers. In fact, it makes absolutely no sense that the Avengers *wouldn't* try to recruit him --- whenever they're trying to save the world from a supervillain that requires teamwork, they're going to need all the super firepower they can muster.