Totally agree. I have a 40" 1080p TV and it looks great. If I had a 4K TV at what point would I see the difference? Well personally I would need to be pretty close to the screen to notice the difference or if the screen size was proportionally bigger the further back I go.
Would I notice the difference between a 50" 1080p and 4K TV from 3 metres away? No I seriously doubt it. So this is where we move into the realm of gargantuan (as you said) 4K screens before we seriously notice a difference.
So what kind of layout is the normal living space for consumers that would buy PS4 Pro? A 4mx5m room with their seats approx 3-3.5m from the TV. Look at the attached chart.
View attachment 1581
For 3 metres away (10 feet), the 4K screen would need to be between 85-90 inches for the consumer to see the benefits of 4K, of course this comes down if they are closer, but for a living space, you seriously wouldnt have your nose up against the screen.
Now how much is a 85-90 inch 4K screen today? We are talking £10k. It does make you think. Probably better investing in a 4K projector and a few extra bulbs.