PS4 wasn't in stores because supply issue. Supply was fixed 6 months later because production was up. PS5 wasn't in stores for 2 years because supply issues and worldwide components problem.
Yes, there was a PS4 supply issue because they didn't have enough semiconductors/chips. It lasted for way more than 6 months, because I remember that months before PS5 launch PS4 and DS4 stock was already minimal or sold out and we initially were thinking that it was because Sony was saving production resources for PS5, but later Sony mentioned the issue with their providers was affecting their shipments.
Unlike PS4 and PS5, at least here in Europe always there has been stock of Switch in the store and at normal prices unlike happened with PS4 and PS5.
Yes we do. 116.2 mil. was as of March 2021. 117 mil. was as of March 2022. See how PS4 sales nosedived during its end of lifecycle?
Yes, as I mentioned as happened with PS5 they barely shipped PS4s since the second half of 2020. The more recent data we have is as of June 30, 2022, shipments being "more than" 117M:
https://sonyinteractive.com/en/our-company/business-data-sales/
As of beginning of 2022 Sony decided to produce 1 million PS4s because PS5 supply problems because of components. Why PS4s? Because surely had chips in stock from previous deal with AMD and TSMC. Also, PS4 sales, like i've said in previous sentence, nosedived. Also worth noting Sony planned to end production of the PlayStation 4 in 2021. But because PS5 problems, it was continued. PS5 supply issues were fixed in 2023 and you can bet that Sony doesn't produce PS4s as much. Maybe PS4 passed 118 mil.
No, in January 2022 Sony debunked these Bloomberg fake news that were saying that PS4 production was discontinued but Sony produced 1M PS4 more to compensate it:
https://hypebeast.com/2022/1/sony-deny-increasing-ps4-production-playstation-5-shortage-report-info
"Nlab: Is is true that the suspension of PS4 production has been delayed due to the PS5 shortages? What is the current production status of the PS4?"
"
SIE PR: It is not true that we cancelled the suspension of PS4 production due to the PS5 shortage. There was no plan to end production of PS4 at the end of last year (2021). The PS4 is one of the best-selling console game consoles for SIE, and like with our past hardware, we produce and sell both old and new hardware in parallel during the generation transition periods."
Meaning, that if they barely produced PS4 consoles during 2021 it wasn't because they had discontinued the console or due to lack of demand. Their plans were to continue producing PS4s, which with recent leaks we saw in late 2022 were 70% of the PS active userbase. Sony also started to merge PS4 & PS5 reported numbers as they also did in other generational transitions and stopped reporting PS4 sales in (sales in March, shipments in June) 2022. As of today PS4 still aren't discontinued.
But yes, I agree that PS4 sales shouldn't be far from 117M. Maybe somewhere between there and 120M.