Sony has posted an FAQ on PlayStation 4 Pro, and while most of the information has already been explained, there was an interesting entry worth pointing out.
In the FAQ, Sony explained once again how games that render below 1080p on PS4 will scale when played on PS4 Pro.
Here's a snippet which explains it much better than I ever could:
PS4 games that render below native 1080p (maximum quality for HD TVs) on the standard PS4 can be elevated to render at full native 1080p on an HDTV. On 4K TVs, games are capable of running at up to 4K (3840 x 2160 pixels, also known as “2160p”) resolution. On HDTVs, games will run at 1080p.
They also provided a chart detailing how PS4 Pro will display based on different TV types.
At launch, PS4 Pro will support all HD video output settings found on the standard PS4. Since it introduces 4K output with settings for both 2160p YUV420 and 2160p RGB at up to 60 fps, it needs a Premium HDMI (HDMI 2.0) cable if used on a 4K TV. It comes with one of these cables, but if you need one longer than what's included, you will have to buy one.
Give the FAQ linked above a read as it is chock full of information.
PS4 Pro releases on November 10.