Sony enabled PS2 backwards compatibility for the PS4 without telling anyone
http://www.techradar.com/news/gaming/sony-slyly-enabled-ps2-backwards-compatibility-for-the-ps4-without-telling-anyone-1309320
"we know the PS4 has the ability to play PS2 games. We don't know how long it's had the capability or how many titles Sony will release, but it exists."