From PS2 to PS3 and onto PS4.
How to Play PS3 Games on the PS4 (with Pictures) - wikiHow
PS4 Backwards Compatibility: Can You Play PS1, PS2, and PS3 Games on PS4?
Is the PS4 backwards compatible with PS3 and PS2 games? - Quora
How to Play PS3 Games on the PS4 (with Pictures) - wikiHow
Games Support
HOW TO PLAY PS3/PS2/PS1 GAMES ON PS4
Can you play PS3 games on the PS4? - here's how!
PS5 patent teases PS1, PS2, PS3, PS4 backwards compatibility
PS4 games SHOCK: PS3 backwards compatibility surprise, could it be revealed TODAY?, Gaming, Entertainment
How to Play PS3 Games on the PS4 (with Pictures) - wikiHow
Is PS4 backwards compatible with PS3 games? - Quora