Very cool.
So with PS4 Pro, they're giving developers the option to take advantage of the power in whatever ways they want, depending on the type of tv you have.
For instance, if it's hooked up to a 4k set, it will run at 4k with HDR. If it's hooked up to a 1080p tv, a game could potentially have Ultra Mode graphics instead of using the power to boost resolution.
They showed Paragon as an example. At 1080p, it showed what the game normally looks like, then with Pro power it showed it with dramatically upgraded lighting, shadows, etc etc. Like Medium settings vs Ultra.
Kind of funny how Cerny started it off saying the current PS4 already maxes out 1080p sets.