“Captain America: The First Avenger” turns out in the end — and this is really the opposite of a spoiler — to have been a two-hour teaser for another movie. That picture, foreshadowed in the second “Hulk,” the first “Thor” and both “Iron Man” episodes and scheduled to open next May, will be called “The Avengers.” Whether you regard its imminence with resignation, dread or uncontainable glee depends on your standing in the Marvel Universe. Shareholders and die-hard fans no doubt already have the opening date circled on their calendars, and many of the rest of us will probably show up as well, either out of curiosity or solemn duty.
