I find 16GB to be too little for something that should last to at least 2026.
I remember very similar discussions back in days before PS4 was revealed, most people were dismissing guesstimates of 8GB RAM and 7970m GPU (which is more or less what PS4's GPU ended up being, with 2CUs disabled for yields).
Yup, 8GB was being completely dismissed back in early 2013 predictions mostly everywhere.
There is no way the PS5 will start at less than 20GB, no way.
$450/500, 14/16TF, 24/32GB RAM, 2TB SSHD/2TB HDD +240GB SSD that's where it'll be landing.
Yeah, Both 8GB and GPU guesstimates were heavily dismissed.
I was one of those who got it mostly right - though I failed to see Jaguar coming as CPU and completely missed about Xbox - I thought there was no way that MS would let Sony have more powerful console after success of X360, but I didn't anticipate them going full retard with focus on TV and Kinect.
As for PS5 and NextBox...well, it's really hard to tell. This is Cold War shit right here, they both want to have better console, yet GPU tech is progressing so slow, especially at AMD. In addition, though current RTX offerings from nVidia don't mean much, it's fair to expect that in 2 years max all their cards will be RT capable...so they have to worry about PC market stealing their thunder, they can't just ignore that.
So, all in all, I expect to see something similar to what happened in X360 era - its GPU had unified shaders way before ATI launched desktop GPUs with same technology...so my guess would be that both consoles will have AMDs equivalent of nVidias RT cores for ray-tracing calculations.
I think they will be failry expensive to make, and that MS and Sony will lose quite a bit in first couple of years on every console sold - 2021 would be much better year for launching, but they will force each other hand for 2020 release.