Benicio Del Toro as an immortal space Elvis
You know the drill by this point. New Marvel movie, new teaser post-credits scene.
This one features Benicio Del Toro as The Collector. Teasing his role in next summer's 'Guardians of the Galaxy' and perhaps foreshadowing a storyline for Avengers 3 (Infinity Gauntlet anyone?).
The Collector is an Elder of the Universe in Marvel comics lore. He is about as old as the universe itself and virtually immortal. He has set up a collection of beings and artifacts as a failsafe against a vision of the future in which all life is destroyed. One of these items is the aether from 'Thor: The Dark World', revealed here to be an infinity gem.
So, that's one infinity gem. Another is revealed to be in Asgard's treasure room (either the tesseract or the gem placed into Loki's scepter in 'The Avengers'). That's two. There are 6 gems total, which when put together create the infinity gauntlet. This item has the power to unmake all life in the universe and has long been the ultimate goal sought by Thanos.
Who is Thanos, you may ask?
Universal terror, Thanos
Thanos is the purple gentleman from the post-credits scene in 'The Avengers'. Thanos is an Eternal in the comics (not as old as The Collector) who is constantly trying to court and impress Mistress Death. And what better way is there to impress Death? Destroy all life in the universe. Thanos is powerful, but not powerful enough to accomplish this feat on his own.
So it would seem Marvel has set the table for an ultimate showdown with the Earth heroes and Thanos over the infinity gauntlet and the fate of the universe. This is probably a few years down the line, maybe a potential storyline for 'Avengers 3', but it's awesome Marvel is thinking so far ahead to tie in all of their movies. And I'm sure 'Guardians of the Galaxy' and phase 2 will expand this even further.
So these post-credits scenes might not make a whole lot of sense yet, but one day they will. And on that day you'll have to tip your hat to the planning ability of Kevin Feige and the Marvel Cinematic Universe.