Ironically with these new consoles coming up, excitement from my end has been coming not from new game rendering technologies and fancy lighting techniques, but from the screens and displays themselves.
I recently had the incredible experience of seeing a JVC DLA-NX9 projector play video games. My friend is a major cinephile and not much of a gamer. The only reason there was an Xbox One S on hand was because he rates it as a great 4k upscaling solution for 1080p movies, and because the HDMI input allows him to upscale even older stuff. He let me sign on and I downloaded FH4 and I was absolutely blown away.
I've played Forza on my GTX 1070 in much higher native resolutions, max settings, with much faster framerates than on his One S. But the colours, the contrast ratio. Also the sound. I always thought headphones were best for gaming, but this is absolutely something else. Native 4k games content is obviously much better, and I was itching to see a sharper image, (if I had £17,000 to drop on a projector I wouldn't be playing on a One S) but there's a point which I hadn't imagined before, which was that great looking games are as much about the display technology as they are about processing and effects.
I read a couple days ago on Forbes that the Series X/S will have Dolby Atmos and Vision, and the PS5 will have Tempest, which if its anything like Vision will also boast around 68 billion colours (exponentially more than HDR10 (8^10 vs. 8^12)) and equally good tone mapping and brightness. Amazing news, but only if you have the tech to take advantage of it. I had been preparing to drop my money on a 3070 or a Series X but I've just gone out and got a great deal on a 2016 enthusiast Sony VPL-HW65. 1080p for just over £1k. My PC will become my game pass machine for the foreseeable.
So that's my "next gen". Seeing the amazing colour and quality that had been there all along. I suspect that many people eyeing up a new console might also need to give some thought to their TV, if they haven't already.