About that semi custom SoC AMD recently mentioned, as it turns out it's meant for Apple (2018).
PS5 might not have a Navi GPU simply because it might be too expensive at the time of it's launch. I'm guessing it will be Vega with features from Navi.
Essentially PS4/Scorpio is an RX 480 GPU, with 4 added CU's for Scorpio instead of the default 36.
Both are downclocked and running at 911Mhz (PS4P) and 1172Mhz (Scorpio) (94Mhz shy of it's max speed of 1266Mhz) respectively.
All Sony would need to do is get a good price on a Vega/Ryzen APU, add 4-6CU's to Vega 64 (68-70).
With the node shrink coming they should be able to push the clock speed to 1340Mhz+ (it's max is 1500Mhz+)
You'd have
70 (compute unite)
* 64 (shader/stream) =
4480 (stream processors)
* 2x 1340Mhz (instructions per clock) =
12TF
I came to this conclusion based on what Microsoft and Sony did with the RX480, the problem here is Vega's HBM2 setup it only comes in 8/16Gb variants.
If Sony does decide to take this route I wonder if we'll see a 16GB HBM2 + 8/16GB GDDR6/DDR5 setup for the OS/streaming assets or if they'll go all in with GDDR6.
Vapor chamber cooling, 7nm/7nm+, and depending on the memory used we could see a more compact system (it really depends on the memory banks used, 1, 2, 4 or 8Gb's).
As for CPU I'm guessing Ryzen 7 (second generation Zen core, so Zen 2) 8core/16threads around 3.2Ghz up to 3.5Ghz, be it the mobile counterpart or not.
This all is in
theory, but based on what the Vega architecture really is (it certainly is an interesting architecture):
https://www.pcgamesn.com/amd/amd-vega-gpu-specifications/#architecture