Anyone who purchases Gears of War: Ultimate Edition or the Xbox One Gears of War: Ultimate Edition bundle will receive all four original Gears of War titles for free by the power of backwards compatibility.
So long as you play Gears of War: Ultimate Edition from August 25 to December 31, 2015, you'll be granted access to the first three Gears of War and Gears of War: Judgment. This comes along with the access to the multiplayer beta for Gears of War 4.
Of course, if you already own any of these four titles on Xbox 360, you will be able to play them on Xbox One with all the features that come with the console like screenshots and Game DVR. Speaking of which, the first Gears of War is actually available today via Backward Compatibility if you are a part of the Xbox One preview program.