This to me seems like a reaction to the continued traction experienced by Sketch, InVision, et al? Now that UX and design has really extended beyond the core vision of Photoshop, this seems like a reactionary move - but perhaps a welcomed one? We're a Sketch shop here, I'd be interested on takes from people using XD today.
No way I'm going to change my system to Windows 10 in order to get this freebie. I also see no reason they couldn't implement a Windows 7 version, the app is pretty basic.