Firaxis teased this very small snippet of a trailer for what looks like something XCOM related. A new game? DLC? They mentioned it was their next big project, so I would wager a guess to the next title in the series. For now, your guess is as good as mine.
Before debuting a teaser trailer for the game during a PAX East panel today, designer Jake Solomon said, "It's big," noting that "we're not going to be able to talk about it for a while."
Also XCOM soldiers will be new units in the next Civ V expansion, Sid Meier's Civilization V: Brave New World: http://www.polygon.com/2013/3/23/4138494/xcom-tech-tree-to-be-added-to-civilization-5