During a talk at a developer conference this week, Epic's Tim Sweeney confirmed the company is working on an "unannounced triple-A shooter" game. This is beyond smaller projects the company has recently been trialing.
It's probably safe to bet though that this new AAA game will be powered by the Unreal Engine 4 and that won't really be out on any gamer's systems for at least another calendar year.
With Unreal Engine 3 now being on Linux, Epic Games historically having their games ported to Linux with the notable exception of Unreal Tournament 3, and more game companies caring about Linux, hopefully this unannounced triple-A game will see a Linux debut.
More details on Epic Games' Tim Sweeney talk can be found at EuroGamer.net.