Hi,
Nintendo is working on their new NX machine. If you look at leaked images it will be like a handheld gaming device which looks a bit like the Wii-U controller. And you can still connect it to a big screen and use it like a regulare gaming device.
I think it would be cool to make a Xbox One S version like this.
So it looks a bit like the Wii-U controller but with a bigger 10" 4K screen. The one like the iPad retina display. You can buy these in China for like $60. And there is a converter available so that you can hook it up to HDMI.
Weight and battery life will be a problem though...