Great news all around, especially for X1 owners with all that free stuff, including a PC code.
I take it we can read the Windows 10 exclusivity as confirmation of DX12? I really hope there's great multi-GPU support, after what a terrible year 2015 was for multi-GPU users.
I think looking at it as Microsoft moving away from console is a bit backwards. This is more about driving Windows 10 adoption, as Nadella recognizes games are the keystone of every digital platform, writing as much when he took the job. The modern model of digital content is to get your products on as many storefronts as possible, regardless of device.
PC gaming will never have the entry price or marketing power to compete with the mass appeal of consoles. Microsoft likely isn't moving to PC or to Steam machines. The Xbox One already is a Windows device optimized for television.
Not to say there won't be any attrition. With DX12, Polaris and all these games, I think 2016 is going to be a huge, huge year for PC gaming.