IFC that in early versions of the script Zemo and Baron Strucker indeed were involved. However, it seemed like a waste to use both so early in the franchise. It's likely that the two villains could show up in Captain America 2 or future Marvel films.
There were a few classic villains that were planned for the first film, only to be removed in subsequent drafts. The pair previously revealed that evil despot Baron Zemo was in an early draft, but he wasn't the only sinister side character in those versions of the script.
"Baron Strucker was in there for a while, but he wasn't doing enough to justify wasting him in the film," said McFeely. "We certainly tried things, and ended up settling on the more useful Red Skull and Arnim Zola. But they're all still on the table," he teased.
"There wasn't a sequence with Master Man that ended up on the cutting room floor or anything," laughed Markus. "But there was an endless array of scenes we could've drawn from, and may draw from in the future. I'm not being cryptic when I say that, either - I'm just being a comic book geek. For example, some day, whether it be in an 'Iron Man' movie or a 'Captain America' movie or any other Marvel movie, I want to see M.O.D.O.K. float down the hall."
Zemo along with creating The Masters of Evil (a group of villains that fight The Avengers) is also responsible for putting together the original Thunderbolts group. The Thunderbolts were similar to the Dark Avengers as they are villains posing as heroes to gain the world's trust and plan to eventually take it over. Other incarnations of the group included villains released from super prisons to reduce their sentences working for SHIELD on different missions. I wouldn't be shocked to see Zemo become a baddie in Avengers 2.
Strucker on the other hand is heavily involved with both Hydra and A.I.M. which could mean that he might be a modern villain that could resurrect Hydra or bring A.I.M. into the forefront. Considering Modok a known member of A.I.M. has been mentioned a few times by the screenwriters. He seems a good bet for Captain America 2 or the Nick Fury film. Hopefully we'll see Madame Hydra ends up alongside Strucker.