Sony would prefer to leave the PS4 generation behind sooner rather than later, were it not for several problems that currently make that impossible. This is according to a recent financial report.
The PS4 still generates more revenue for Sony, and PlayStation Plus has a significantly stronger presence on the PS4, even though interest in the PS5 is considerably higher than it was for the PS4 at the same time. The following graphic illustrates this. However, the PS5 boasts more playtime and transactions, which should encourage Sony to aggressively promote the PS5 more than ever.

In concrete terms, this means that Sony still generates 65 percent of PlayStation's revenue on the PS4. 69 percent of all PlayStation Plus players are also still on the PS4, which, from a business perspective, doesn't justify simply abandoning the last-gen consoles.
While the PlayStation 4 may be a popular console, many would still switch to a PS5 immediately. The problem: availability is notoriously difficult and will only ease somewhat in the coming months. According to AMD and Intel, the situation will remain critical at least until 2024.
PS4 will likely be supported for longer.
This is also good news for PlayStation 4 users, who will likely receive new games for much longer than initially planned. Sony currently expects PS4 games to be produced and released until 2025. However, it's also noticeable that more and more last-gen projects are being canceled, most recently, for example... Gotham Knights or Test Drive Unlimited: Solar Crown.
By the end of the fiscal year in March 2023, the company plans to have shipped approximately 34 million PS5 consoles worldwide. It remains unclear whether this will be enough to meet demand, as the graphic above also shows that the PS5's sales rate is significantly higher than that of the PS4 at the same point in its release.

I don't know, most games still look like they would work on a PS4. Demon's Souls would also run on a PS4; after all, the original game with its linear levels ran on a PS3. There's no technical limitation besides loading times that would prevent it from running.
Ratchet and Clank would also work; switching worlds sometimes involves animation, so it's not instantaneous. This could be replaced or introduced with a rendered video.
Much of it is just PR fluff and attempts to lull customers into complacency.
The PS5 won't even come close to the PS4's sales figures. Publishers are gone, PS games are coming to PC, fans are completely ignored, there's no interaction with fans or news flow, and PS5s are nearly impossible to find. Etc., etc., etc. I want Ryan and his ilk's drugs too.
I think the reason the PS5 isn't selling as well as hoped is more likely due to the supply situation. It took me over a year to finally get one.
However, the reasons that led to this are all homegrown and are being frenetically celebrated, especially in this country.