ReCore will launch Sept. 13 according to a leak of assets uncovered by NeoGAF in advance of the Xbox E3 presentation.
The Windows and Xbox One exclusive from Keiji Inafune's Comcept studio was revealed by surprise at E3 2015 and given a spring 2016 launch window. That was moved to a generic 2016 date back in January. There's a good chance we'll be seeing more of ReCore in Microsoft's keynote tomorrow.
A couple of screenshots (above and below) also slipped out. For more on ReCore, see Polygon's in-depth look at its creation, carried off largely in secret, from E3 2015.