You can get "true 4k" out of the console, but rendering at 4K is so taxing you'll chew all the extra processing power out of that GPU. That means that if developers want to increase rendering quality other than spatial resolution, they will probably resort to checkerboard rendering and/or dynamic resolution, which they needed to do on PS4 Pro. Of course, overall, you can probably expect better quality than a PS4 Pro, since there's more power. It's just not very wise to use that to output at 4k, especially when most people will have a hard time noticing the difference at living room distance from their TV.