Sony has already started R&D on the PS5

[Arkaign]

It's sort of semantics, but they aren't REALLY working on a PS5 at this time. What they are working on is a continual series of examinations and tests of ideas and emerging technologies balanced against economics. As the target date gets closer to reality, they will begin to firm up spec, design, philosophy, and budget.

I hope they stick with x86.

In a way, it sucks that 2013 was D-day for gen8 with MS/Sony. The Jaguar CPU and die size were a couple real sore spots. The upcoming Zen CPU, even in a 4-core variant, would have enabled DRASTICALLY more powerful consoles at the same price.

In Gen7, dev obstacles were :

differing architectures between the big 3
early multicore utilization with PS360
LOW MEMORY, be it 512+10 or 256+256, that was the big one

In Gen8 those obstacles are nearly eliminated beyond any doubt :

only Nintendo remains non-x86, but it's almost a fundamentally 1st-party only console, so it is fine for that
multicore utilization has improved dramatically, and will continue to do so (partially because a single Jaguar core is garbage)
Plenty of memory, and it's not segregated (the OS/reserved amounts are kind of stupid, but whatever).

But now we have new limitations :

Terrible per-core/IPC performance (all 8 Jaguar cores together are notably weaker than 2C/4T i3)
More overheads from background OS/App nonsense

On balance, PS4/X1 are of course better, and suffer fewer limitations compared to PS360 (the ram issue being a massive one), but a holiday 2015 X1/PS4 could have been bananas at the same MSRP.

Looking at all the cross-gen releases, and the maturity of the PS360 APIs, I would have even preferred it TBH. So many games for PS4/X1 could have been done on PS360, even the exclusives, albeit at reduced clarity. But some say they can't tell the difference anyway, so all the better, right?