Panajev2001a
GAF's Pleasant Genius
Could it be the next Sony machine isn't PS5, but a PS4 Ultra, something just strong enough to surpass X1X? That is something I could see happening in 2018 or 2019, if it does at all.
Personally, I think the next Sony console will be PS5. I think the announcement could happen between December 3rd 2019 (25th anniversary of PS-X released in Japan) and February 2020.
If Sony believes in console generations having one extra per generation iteration is quite enough. It costs a pretty penny to design these machines and put them in production and I do not think Sony will massively change their plans now because of Xbox One X. Better to focus on PS4 generation games and developing HW and SW stacks for PS5.
I still disagree with you massively on Sony relying on another 7-8 years generation not to hurt the launch of PS5 massively, it is a huge risky gamble made worse by MS iterative dreams.