Riding a generally positive wave of buzz following the Super Bowl teaser for the Captain America: The First Avenger movie, Marvel is keeping things flowing by commissioning the screenwriters of that film to start working on a sequel script. The pair are expected at this stage to write something that will be taking place in the modern day since Cap will be in the Avengers film and this one is very likely to take place after the Avengers move in terms of in-movie continuity (though depending on how they deal with the timeline in the Captain America movie, anything is possible). Marvel has an aggressive schedule this year and has two big projects lined up thereafter with the first Avengers movie and work starting on getting things together for Iron Man 3 in 2013, which is also when a likely sequel would appear for Captain America.
Chris Evans currently has a contract similar to other recent actors in that he's tied to a six picture deal, though that includes work in non-Captain America movies such as the already slated Avengers, and he's likely to be pretty game for a sequel with the positives he's hearing about how things look from the teaser trailer.
What story would you want to see in a modern-day period Captain America movie? Or would you prefer them to sneak in a side story from the World War II period to flesh that out more?