Update, 2:50 p.m. PT: In a post over on PlayStation Blog published earlier today, Senior Vice President of Platform Planning and Management at PlayStation Hideaki Nishino further detailed the current progress of PlayStation 5's backward compatibility.
"We recently took a look at the top 100 PS4 titles as ranked by play time, and we're expecting almost all of them to be playable at launch on PS5," clarifies Nishino. "With more than 4000 games published on PS4, we will continue the testing process and expand backwards compatibility coverage over time."
Seemingly similar to Microsoft's own Backward Compatibility service, it appears that PS4 games will be compatible with the PlayStation 5 architecture on a roll out basis as they're tested, rather than a blanket "everything you've ever owned on PS4 automatically works" sort of system.
The original article continues below.
During a PlayStation presentation that was originally planned for the Game Developers Conference, PlayStation 5 lead system architect Mark Cerny confirmed that the PS5 will indeed be backward compatible with PlayStation 4 games. This includes ones with bonus performance and fidelity features for PS4 Pro. It's all thanks to the PS5's highly sophisticated-and more cost effective-chip.
If you remember, the launch edition of the PlayStation 3 was backward compatible with PlayStation 2 games. During his talk, Cerny says that it was an "expensive" decision, considering it required an extra chip. For the PS5's backward compatibility, the architects at Sony have a more savvy solution: the chip for the PS5 will include a "legacy mode" that lends compatibility with PS4 games. It won't need those extra chips. Unfortunately, it's bad news for fans who were maybe hoping for deeper backward compatibility into the back catalogue for earlier PlayStation consoles.
In a full-write up pre-livestream, our friends at Digital Foundry lay out all the specs behind the PS5. Similar to the Xbox Series X, the PS5 will have an extra slot for M2 drives for additional storage-only here it's ones that are "off the shelf" and approved by Sony, though not fully proprietary like Xbox Series X's or PS5's internal SSD. In its breakdown, Digital Foundry advises that players can "save space by running your older games from standard external storage. It won't be as fast as booting from the internal SSD, but it'll free up space for the next-gen titles that are going to need it."
In February, Ubisoft CEO Yves Guillemot confirmed that both Xbox Series X and PS5 would be backward compatible in an earnings call. "Those consoles will be running almost all the back catalog of the previous consoles," Guillemot said. "It will be something new in the industry, it will help the old generation to continue to be big consoles on the market in the years to come."
The PlayStation 5 is due out in holiday 2020.