Members of the official Gearbox forums have spotted some promotional material for Aliens: Colonial Marines in Walmart, one of which reads “Team up with your friends to take on waves of increasingly difficult enemies in an all-new game mode”, by the name of “Bug Hunt”.
The image continues “Available March 19, 2013 via download”. So! Seems like a pretty open-and-shut case here: Aliens: Colonial Marines is getting a horde mode DLC next month. For $14.99 (or rather, probably $25 for Australians).
As the original poster on the Gearbox forums points out, “$14.99 value” indicates that it could be free for some users, or perhaps bundled free with something so that people can be charged $14.99 if they want to buy it separately later. What do you think? Horde mode seems a natural inclusion for me, especially against the xenomorphs.