This is what I reckon. There's been a huge amount of New Gods stuff in a lot of the books recently (Earth 2/World's End, Future's End, Batman and Robin, Godhead in Green Lantern, Infinity Man and the Forever People, Darkseid War in Justice League), and I find it hard to believe it's not all co-ordinated to reach some big Crisis Anniversary event later in the year. Providing Darkseid War is just a prologue to the event a la Trinity War, then it's not hard to believe it'll only be 3 issues.