1.) None beyond PS4.
Digital only BC:
2.) Rebooted PS2-on-PS4-like program.
-PS1
-PS2
-PS3
3.) Expanded PS2-on-PS4 program.
-PS1
-PS2
-PS3
Physical and Digital:
4.) Full Backwards compatibility:
-PS1
-PS2
-PS3
What do we expect?
This far level 1 is the only thing that has been confirmed.
2 or 3 seem likely.
4 is the dream, but I doubt it'll happen.
Digital only BC:
2.) Rebooted PS2-on-PS4-like program.
-PS1
-PS2
-PS3
3.) Expanded PS2-on-PS4 program.
-PS1
-PS2
-PS3
Physical and Digital:
4.) Full Backwards compatibility:
-PS1
-PS2
-PS3
What do we expect?
This far level 1 is the only thing that has been confirmed.
2 or 3 seem likely.
4 is the dream, but I doubt it'll happen.