<p>Well, the end of <i>First Avenger</i> is a clear set-up to bring Skull back. However, at the time the MCU was still getting off the ground and I'm fairly sure that Mr. Feige couldn't have reasonably had enough confidence to seriously plan out plots twenty years ahead (which he has now, but in the intervening period the MCU has become probably the single most valuable franchise in terms of expected <i>future </i>revenue currently in operation, if not of all time). So, I think at the time of the first Cap movie, Skull's comeback was a <i>possibility</i>, as it tends to be in most films that expect possible sequels, but are waiting for box office to be sure.
</p><p>By now though, I wouldn't be surprised if there already were a concrete plan, if not agreement with Mr. Weaving, to bring Skull back. Perhaps in "Captain America: Civil War"? By the sound of the title, that movie should be a big showdown between what's left of Shield, plus Cap, and the newly upstart Hydra as set up by Agents of Shield and Winter Soldier. So, the Skull would be a logical adversary for that movie, being the Cap's natural nemesis, and considering that Strucker probably isn't gonna be a distinctive enough character to pull off lead villain in a major movie.
</p><p>(The latter is not meant as lack of faith in the actor; rather, the Strucker character is not really well positioned as a main villain: no superpowers, not hyped up enough, etc. He's probably a good side villain for Age of Ultron, and potentially a very good main villain for Agents of Shield (a "normal" evil bstd for the "normal" agents on the show to fight would probably have more impact than a superpowered villain, too: it would kind of legitimize the normal agents' presence in the universe, sort of a "you Avengers fight the aliens and other crap, while we ordinary guys take care of the bad-enough stuff some humans can do" division of labour).)
</p><p>In any case, I'd like to see the Skull back, if nothing else then for Mr. Weaving's excellent portrayal of a credible (if you let slide the skull-for-a-face thing, anyway) and interesting villain. In particular, I liked the fact that the Skull did not believe his own propaganda -- Weaving's portrayal made it quite clear that he considers that little more than a formality; he's bluntly interested in absolute power, and the mystical-slash-supremacist crap that Hydra regularly spouts is just a tool to him. Unfortunately for the heroes, this makes him <i>more</i> dangerous.
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