Epic Games' Cliff Bleszinski believes very strongly in the PC gaming market, as he considers it the next gen. To prove his point, the studio's upcoming Fortnite is a "PC game first and foremost."
Fortnite is going to be the first Unreal Engine 4 game and remains Epic's priority right now because of that. This is the chance to show the world what UE4 is capable of, and Cliff Bleszinski and the rest of the team at the studio don't want to disappoint. He has repeatedly said the next gen systems are already here in the form of high-end PCs, which is a terrific statement from a studio that seemed increasingly console-centric.
The studio plans to have a beta for Fortnite available in 2013 and will be listening to everything the testers have to say. Fortnite is a zombie survival game heavily focused on constructing fortifications, so if there is anything that doesn't seem quite right, beta testers can let Epic know.
We don't have a solid release date or confirmation of mod support at this time, but hopefully all of that gets settled before long.