There's been no official confirmation yet, but there are apparently people playing the game right now, and a video has appeared of multiplayer.
Update: Footage of the game in action have appeared on ElitistPath05's Xbox clips page. You can watch it here.
Polygon reported yesterday that they have received information about the apparent remaster. The title will apparently be a remaster of the original title, and it will release for Xbox One with a new coat of polish. Their story has since been updated to say they have been shown screenshots from people who are playing the title, but Microsoft has yet to confirm whether or not the story is actually true. They also were told that Splash Damage (developer of last generation's Brink) is making the remaster.
Earlier this year, Rod Fergusson (who used to work at Epic Games, and is now the studio head at Black Tusk, which is making an actual new Gears of War game) cut down rumors that a "Marcus Fenix Collection" was in the works, which would have been in the vein of last year's Master Chief Collection.
The last Gears of War title to be released was 2013's Gears of War: Judgement, a prequel. According to Fergusson's tweet, we can expect to see Black Tusk's brand new Gears game at E3 this year.