Real HW compatibility for PS3 would make PS4 to expensive. The SW emulation is actually porting game after game... majority of the gamers don't really care about it, they proved it when they removed PS2 compatibility.
So I wouldn't even expect PS5 to be BC with PS4.

duduspace11 "Well, since we are estimating costs, Pokemon Red/Blue did cost Nintendo about $50m to make back in 1996"
http://gamrconnect.vgchartz.com/post.php?id=8808363
Mr Puggsly: "Hehe, I said good profit. You said big profit. Frankly, not losing money is what I meant by good. Don't get hung up on semantics"
http://gamrconnect.vgchartz.com/post.php?id=9008994
Azzanation: "PS5 wouldn't sold out at launch without scalpers."







