One source (for its safety, I will not indicate its name), said that the Playstation 5 will be compatible with PS 1, 2 games through software emulation (modified versions of PCSX and PCSX2 emulators will be used). Playstation 4 will work natively, without emulators, as the Playstation 5 will have a similar architecture to the PS4.
However, the Playstation 5 will not be compatible with PS3 games. A source said that the architecture of PS3 is rather difficult to emulate on the new hardware of PS5, therefore compatibility with PS3 games will not be available at the launch of the new console from Sony. However, it is possible that we will get some “moded” PS3 games in the PSstore after the release of PS5.
I would like to remind you that Sony is using emulators not for the first time. PS1 Classic released in 2018, used a modified PCSX repository.
It should also be noted that Playstation 4 did not have backward compatibility with any of the previous generation consoles (several games “remade” in the PSstore is not an option when you have a huge library of games at your home).
In the meantime, while you are waiting (like me) for the release of Playstation 5, you can see a list of the best PS4 exclusives. Perhaps you missed an interesting game.