Back in July at Comic-Con, Entertainment Weekly caught up with VanCamp (and a few other Cap 2 actors) and she briefly spoke about her upcoming role in the Captain America sequel.
"We're just sort of, like, planting the seed for my character," VanCamp said. "So I'm not in the film as much and I'm just now meeting some of the people from the film to be honest."
What this "seed" is remains to be seem but it definitely implies that Agent 13 will have a growing role in the Marvel Cinematic Universe in future movies. The obvious choice is she could appear in Avengers: Age of Ultron after Cap 2.
Reasons why VanCamp was chosen for the role were also discussed in Total Film, but the Russo Brothers.
"We wanted someone that Cap would have an immediate interest in. It had to be a strong-willed person, and we felt that Emily’s work on Revenge was a great test tube for what this character could be. She’s obviously very credible with physicality, she holds the screen really well, and she even looks like the character from the books."
In the comics, Agent 13 (a.k.a. Sharon Carter) is a relative of Peggy Carter and she also has a relationship with Steve Rogers in the comic universe as well. This is just a thought but it might make for some interesting drama if in Captain America: The Winter Soldier Agent 13's involvement also creates some tension for Captain America and results in some kind of love triangle between the Cap'n, Black Widow and Agent 13.
Captain America: The Winter Soldier releases on April 4, 2014.