I think all 4k TV's upscale sub 2160P content up to 4k anyway, so with the Xbox One S, it is just done internally within the console before being sent out to the TV. The only real benefit of this is less input lag as it is being upscaled prior to being output. So I'm assuming the PS4 Slim on a 4K TV will 'look' the same but maybe features a tiny tiny bit more input lag?? Maybe someone can clarify.
The HDR issue will be seen when Sony put out the HDR patch covering all PS4s, which 99.9999999% of people thought was impossible to do because of the HDMI being rated at 1.4...







