PS3 isn't holding anything back except maybe some Interface improvements. Even then it could be separated from the PC/PS4 versions. They already have done this. So no, the PS3 is a scapegoat, not a reason. Dropping it would kill part of their user base, and in turn their income. The major thing holding most requests back is server to client communication. So blame the architecture, and while blaming it, realize it isn't going to change without a major overhaul (which again will cost money that they don't see a need to spend.)