Adinnieken on 21 December 2011
The PS4 won't be Cell-based, so it's possible that they could build in an emulator. However, going by Sony's patents from two years ago, I think it's more likely that Sony will release PS2/PS3 modules for the PS4 that include actual hardware for full compatibility to both systems and that physically plug into the console itself.
Again, this is based on official patent requests, not pure speculation.
