Update - August 31: Ubisoft has now removed a line regarding PS5 backwards compatibility support for PS3, PS2, and PS1 games from its next-gen support page (opens in new tab). It previously read: "Backwards compatibility will be available for supported PlayStation 4 titles, but will not be possible for PlayStation 3, PlayStation 2, or PlayStation games."
It's unclear why this line was removed, but there are several plausible reasons, the most obvious being that Sony may not have liked it. It's possible that this information is outdated, or perhaps it only pertains to Ubisoft games and Sony wanted the publisher to avoid potential confusion. This is unlikely, but quite frankly everyone is stabbing in the dark at this stage. In any case, as we've laid out below, legacy console support on PS5 remains a pipe dream for the time being, and that won't change until Sony says otherwise.
According to a new Ubisoft support listing (opens in new tab), PS5 backwards compatibility will not extend to PS3, PS2, and PS1 games.
This isn't an official PlayStation statement, but Ubisoft is a big and established partner, so this is pretty clear. Sony has yet to outright dismiss PS3, PS2, and PS1 support, but it's only ever discussed PS4 games with regards to PS5 (opens in new tab) backwards compatibility. In other words, the writing has been on the wall for a while, and this is just Ubisoft reading it to us. Physical and digital PS3, PS2, and PS1 games won't be playable on PS5, except through PlayStation Now, which we already know to be coming to the console.
Hopes for older console support on PS5 first flared up in February 2019 with the emergence of a Sony patent (opens in new tab) related to emulation technology. The gist was that this technology would enable the PS5 to simulate legacy consoles and, conceivably, run older games. Of course, patents don't always materialize, and the exact range of "legacy consoles" was never clearly defined.
The first public mention of PS5 backwards compatibility (opens in new tab) was given at system architect Mark Cerny's March tech talk. PS3, PS2, and PS1 were conspicuously absent from this portion of Cerny's presentation, which didn't bode well for older consoles. However, with Xbox pushing four generations of games on Xbox Series X, some held out hope that Sony would integrate backwards compatibility more heavily as well. The way the two platform holders have approached backwards compatibility also reflects their generational outlooks, with Xbox building an ecosystem and PlayStation pushing for a clear generational leap.
Here's what we know about Xbox Series X backwards compatibility (opens in new tab).