ReCore was announced back in E3 2015 to an audience that couldn't have possibly seen it coming. Nobody had leaked the existence of the game beforehand, nor did the storied and beloved developers behind the game even hint to their fans that they were working on a new project. Suffice it to say, ReCore is going to be a huge deal when it ends up releasing - and it turns out we may have an idea about when that's going to happen.
While the source of the information was since removed, Polygon has reported that NeoGAF leaked out some info that pegs ReCore for a September 13th launch date in North America, and on September 16th in Europe. We'll almost certainly find out if this info is valid when Microsoft gets on stage to do their keynote tomorrow - and frankly, the smart money is on this being legit. Leaks this close to E3 have a habit of being fairly on the nose.
Since the only release window we have for ReCore right now is just "the latter half of 2016" and we're going to likely see quite a bit more about the game during E3, the September release date makes sense. We'll see if the leak ends up being on point.