So proceed at your own peril.
Despite there still being one more film to be released before The Avengers: Age of Ultron brings Marvel's Phase 2 to a close it seems likely that Guardians of the Galaxy will be letting the currently established universe take a breather following the events of TWS and will instead focus on building the foundations for Phase 3 films.
Which means that once again it is the events of Cap's standalone story that will lead us into the big crossover of the Avengers, and as such it falls to the films (primary) post credit sequence to set the stage.
The scene shows Baron Von Strucker (Thomas Kretschmann) a leader of a Hydra facility reacting to the news of the destruction of both Hydra and SHIELD (Those spoilers I warned you about), it is shown that Hydra have possession of the staff Loki wielded in The Avengers (having seemingly acquired through their influences within SHIELD) it is implied that Hydra have been using the staffs energy to perform experiments on people which has resulted in the deaths of all test subjects bar two a boy with Super Speed (Quicksilver - Aaron Taylor-Johnson) and a girl with telekinetic abilities (Scarlet Witch - Elizabeth Olsen).
Now this scene is seemingly important for a number of reasons, firstly it serves to introduce audiences to Cap comic villain Baron Von Strucker as well as the Twins for the first time all three of which will feature prominently in The Avengers: Age Of Ultron.
And secondly it answers a question that I had not even thought to ask yet:
Just what happened to Loki's Staff?
This in turn is more of an interesting issue than I first considered due to just how little information we have received about it:
- We know that Loki received the staff from Thanos (The guy who appeared during the post credit scene of The Avengers).
- We know it allowed Loki to take control of people.
So to see that it in fact has a whole other array of powers is fascinating, especially since rumors have begun to surface that the blue jewel at the head of the scepter is one of the infinity stones used in Thanos's Infinity Gauntlet (Rumors state that it may be the Mind Stone).
A brief summary of the Infinity Gauntlet: The Gauntlet grants the bearer infinite power over reality through the use of the six Infinity Stones (Mind, Reality, Soul, Time, Power, and Space)
and Thanos (That lovable rouge) is trying to collect the six stones, two of the infinity stones have already been introduced in previous Marvel movies.
Another Pro of further exploration of the staff's powers is that Scarlet Witch and Quicksilver's are able to have their origin stories tweaked, as in the comics they are of the mutant offspring of the X-Men villain Magneto but since the X-Men, Magneto and the twins origins are all owned by '20th Century Fox' Marvel and Disney are not able to use these specific details (plus it would make very little sense anyway since the X-Men universe are about to get their own version of Quicksilver in Days Of Future Past) so the staff experiments are an effective way of both introducing the twins power while altering its origin.
So of all the current Phase 2 post credit scenes from Iron Man 3's last minute cameo to Thor: The Dark World's introduction to The Guardians of the Galaxy, TWS seems to raise the most possibilities for the longevity of the franchise and while it mainly serves to set up Age Of Ultron it is impressive to see Marvel potentially lay the groundwork for films that may be five of six installments down the line.