In the past, Sony has been adamant that backwards compatibility for PlayStation 3 (PS3) games would not be coming to the PS4. We've seen it with its European boss Jim Ryan stating so in June of this year. The topic presented itself again during Paris Games Week, forcing Shuhei Yoshida, President of Sony's Worldwide Studios to reconfirm the same.
As for getting PlayStation 1 (PS1) and PlayStation 2 (PS2) games working on the PS4? This seems to be likely. According to website Gearnuke, classic PS2 games like Ape Escape, Dark Cloud, and Twisted Metal: Black were rated by the Pan European Game Information (Pegi) - the video game classification system for Europe. This is backed up by a patent spotted by leading game forum NeoGAF that allows Sony to add trophy support to PS1 and PS2 games.
Furthermore, certain PS4 bundles for Star Wars Battlefront include a digital voucher for four classic Star Wars games. Three of them were previously on the PS2. These include Star Wars: Racer Revenge, Star Wars: Jedi Straighter, and Star Wars Bounty Hunter. The fourth game is Super Star Wars, a game that was on the Super Nintendo Entertainment System (SNES). All of them sport enhanced graphics and trophy support for the PS4, making PS1 and PS2 playback for the PS4 a whole lot more certain.
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If true, it's a smart move from Sony. PS3 owners who bought classic PS1 and PS2 games should be able to transition their digital purchases to the PS4, while those new to Sony's ecosystem can experience some of the greatest hits of previous generations. Also, it's a smart way to combat the Xbox One's backwards compatibility with Xbox 360 games. With Sony's US-focused PlayStation Experience event slated for December 5 we won't be surprised if we see an official announcement in the coming weeks.