Rumors surrounding the ongoing development of Sony's next-generation console, expected to be the PlayStation 5, are already swirling despite a likely launch in 2020 or beyond. This morning a patent filed by Sony in Japan implies that the company's in-development console may have digital backward compatibility, potentially supporting not just PS4 games, but possibly even PS3, PS2, or even games from the original PlayStation.
Obviously, this doesn't mean that anything whatsoever is confirmed. A patent is just a patent (a legally registered idea) and doesn't always come to fruition. The terms in a patent are also intentionally ambiguous, which could mean that even if the patent is used it could be used in an entirely different and unexpected way. Nevertheless, given the ongoing development of the PS5 the patent does imply what Sony could be seriously considering backward compatibility for its upcoming console.
The patent doesn't explicitly name the PS5, of course. It references instead an ambiguous future machine or platform, powerful enough to employ a technique known as CPU spoofing in order to digitally recreate older consoles. CPU spoofing meaning that the actual CPU creates a digital version of an older CPU through emulation. This new platform would test to see if an application is intended for a "legacy device" and if so would spoof the legacy CPU and run a special routine to minimize synchronization errors stemming from the speed differences between the two CPUs.
Historically, this kind of emulation for older devices has been extremely challenging, which is why it's not seen very often in consoles. Older consoles, from the original PlayStation through the PS3, have very unique architectures that make spoofing incredibly challenging. Compound that with newer consoles having somewhat limited CPU technology themselves and that's why CPU spoofing and backward compatibility with much older consoles is rare.
With the PS5, and likely the next-gen Xbox as well, consoles have finally reached a point where CPU spoofing is completely realistic. It's not going to be simple (just look at how the Xbox One's slowly adding backward compatibility title by title), but it's absolutely possible. Not only will the PS5 be powerful enough to emulate much older consoles, but it'll almost certainly have an extremely similar architecture to the PS4. That means that a PS5 could, if Sony chose to support it, offer backward compatibility with all earlier PlayStation consoles.
Whether Sony chooses to support backward compatibility is another matter entirely. Rumors insinuate that Sony is at the very least considering PS5-to-PS4 backward compatibility to maintain the current era's expectations. Beyond that is another matter entirely.
Sony is typically very protective of its works. After all, it did offer a version of the PS3 that was backward compatibility with the PS2 at launch but decided not to run with it. Backward compatibility could prove a defining feature of the next generation of consoles. Sony seems to be preparing for any possibility, but what becomes official is anyone's guess.