Scorpio is also more powerful, however it looks like they are trying to pull an Xbox 360 on microsoft and launch something good enough but earlier.
Neither Scorpio nor PS4 pro would actually do 4K gaming, they will however most likely will have no issues of doing true 1080p gaming at 60fps which is considerably better than either of the consoles can pull off as well as maybe a few 1st party / indie titles at 4K.
I don't actually think the UHD BluRay is going to be an issue, BluRay sales aren't exactly have been great in general and considering that UHD BluRay movies tend to cost about double I don't see the sales being that great.
Streaming 4K however should be considerably more important as Netflix and the likes are getting more and more UHD content you would want your console to be able to catch up.
Project Scorpio will, the PS4 Pro won't support 4K gaming either, even a GTX 1080 won't do 4K @ 60 well with modern titles.
The PS4 Pro will be a 1080p @ 60 console but nothing more regardless of how they are marketing it, the GPU it has is between the RX460 and the 470 in terms of performance and while they can push for 1080p @ 60 on medium/high settings* on most modern titles they can't run anything at 4K at playable framerates, not even "console experience" frame rates.
*New upscaling techniques like UbiSoft's Checkerboard Rendering with decent Temporal AA/EQAA will be able to upscale some games with minimal image quality loss.
UbiSoft renders Rainbow Six: Siege at 960x1080 and upscales it to 1080p.
And the Xbox One and PS4 have been shown playing games at 1080 during their launch events so what?
The amount of games that are doing 1080p on either console is slim, they render often at sub 900p (especially on the Xbox One) resolutions with FPS locks to 30.
When the Xbox Scorpio was announced which is still more powerful than the PS4 Pro most developers said they'll use the extra power to run the games at 1080p with higher settings than aim at 4K gaming.
They will end up doing upscaling of some sort, they have gotten pretty good at it but true 4K pffttt dream on.
I agree that Xbox one doesn't have many 1080p games however how does it follow that ps4 does not? Except for few games like AC, which decided to keep parity, pretty much all ps4 games are 1080p.
They said that the 4k is achieved via upscaling. There's basically interpolation on 1080p with the additional pixels to create a nice visual. So it helps with aliasing issues and gives a crisp look, but neither console is capable of actually rendering in 4k.