Sony Interactive Entertainment (SIE) CEO Jim Ryan has expressly stated that there will be no backwards compatibility (BC) to the PS1, PS2, and PS3 for the upcoming PlayStation 5. However, just as the PS5 BC question appeared to be put to bed, social media commenter HipHopGamer claimed that disc-based full BC was still a thing.
https://www.notebookcheck.net/PlayStation-5-backwards-compatibility-question-creates-unlikely-conflict-SIE-CEO-Jim-Ryan-vs-gaming-personality-HipHopGamer.494606.0.html