I just dont see Sony trowing into the toilette millions of PS4.... They'll try whatever to keep forward compatibility at least for a couple of years after next gen release. So next gent still Jaguars maybe 16 cores, maybe 3 ghz... Maybe even bettered at 7 nm....
Sony most probably isn't putting BC in danger if they still go with x86-64.
As for using Jaguar instead of Zen in the PS5, at 7nm we should think if the performance/area of Zen-based CPUs would be that much different from Jaguar-based CPUs.
I think it's not, to be honest. And the only reason we didn't see Zen cores in the XboneX is because the console had a rather long development time so Zen cores weren't on time.
The Jaguar CPU complex in the PS4 Liverpool is
52mm^2 at 28nm. I don't know how much it occupies at 16FF, but some 30mm^2 is safe to assume.
A
4-core Zen CCX is 44mm^2 at 14FF. At 7nm we're probably looking at around 25mm^2. That would mean two Zen CCX at 7nm would be around 50mm^2, which is about the same CPU area budget the original PS4 had.
Cut down hyperthreading and L3 cache (not really useful in games and mostly used for coherency among CPU cores?), and I'd say 2*CCX Zen cores would be at around 40mm^2.
However, there's rumors about the Zen 2's CCX now being of 6-cores. In that case, maybe a single CCX with hyperthreading at ~3.5GHz would be more than enough to "emulate" the 8 Jaguars @2.1GHz.
One thing console SoC makers should definitely be looking at IMO is heterogeneous CPUs. A couple of ARM Cortex A55 cores at 1.8GHz (or Jaguar cores if they definitely have to maintain instruction set?) would probably be more than enough for the O.S. tasks, leaving all of the bigger Zen x86 cores available to the developers. They could have low-power O.S. cores independent from the App/Gaming cores, and the latter could even be treated as co-processors for the O.S.
