With Thor and Captain America: The First Avenger both being pretty big critical and finacial successes, alongside Iron Man and it's sequel as well as The Incredible Hulk it looks like the Marvel Cinematic Universe can't be slowed down (except in those awful games) and with five films up, and one more confirmed to go I thought now would be a great time to begin speculating about the future of the universe and The Avengers. Be warned there will be spoilers for all the movies in here, so read at your own peril.
Captain America Villains to Threaten the Avengers
All of The First Avenger goes out of it's way to play up the Red Skull as something of a shadow archetype to Cap himself- he's what the good Captain would be if he were a twisted evil individual. To further the symbolism and archetype comparison- remember at the end of Captain America, during the two's final battle, when Red Skull uses the Cosmic Cube? It looked more like a miniature Bifrost Bridge than a disentegrator to me, and we've seen that each of the realms has it's own version of the Bifrost in this universe via the Thor: God of Thunder video game. My own theory is that Red Skull ends up transported to Jotunheim, where he ends up being frozen in the land of the Frost Giants. 70 years later, during the events of Thor, near the end when Loki attempts to turn on the Bifrost Bridge on Jotunheim in his attempt to completly destroy it clearly tore up the landscape- but didn't destroy everything before Thor stopped him. I think Red Skull was uncovered here during this moment, and was either only unfrozen later, as a sequel hook to Avengers (Maybe with Loki finding him, and beginning to plan a big "Masters of Evil" type thing?) or Red Skull could turn his conquest on the Jotuns, who are both leaderless and destroyed, essentially being left in the same condition as Germany was when the Nazi party took it over- so at least Skull has experience with that.
I also think it's possible for Arnim Zola to survive into the present day in a sense. We saw his classic robot body in the Captain America: Super Soldier video game. I think it would be possible for Arnim Zola to preserve his work at the very least, and possibly more, in an advanced AI that lives in the suit, leading to the classic Arnim Zola we all know and love. It would obviously have to seek out upgrades to keep up with the advancement of technology over the years. Added irony- Zola could be armed with upgrades purchased from Stark during his weapon making days, which could connect him to two of the Big Three. Outside that- I hope Iron Cross comes back as a new person under the suit at some point in the continuity, though I doubt we'll ever see him again.
Hulk Will Actually Stay On This Team
We all know that Hulk's history with the Avengers is a short one in the standard continuity, but even with Earth-199999 Hulk getting the short end of the stick, it still seems like it would be a waste to introduce the character, and even keep Abomination alive for the future, if Hulk is just going to storm off and leave the team. Plus, Hulk seems like a character Joss Whedon would have lots of fun with, so there's that on a more meta level.
What about you guys? Any theories where the next movies will be going? About how the current movies will tie in together?