It's great that these movies feel like parts of a greater universe, that they affect each other and feed into each other. I think there's a nice progression in the past four films -- Fury fills in Tony on the Avengers Initiative, then Coulson splits off to deal with the Asgardian incursion, which brings in Selvig, who gets introduced to the Tesseract; and then we flash back to the story of how the Tesseract came into play, which is also the backstory of Captain America; and then all those threads come together when Loki invades. It's very deftly done.
Right. A JLA movie out of nowhere is absurdly reactionary.
They need a plan as opposed to retroactively sticking their existing movie characters into a movie.