If SE does the right thing with the PC and PS4 releases it can still sell good on those platforms. Launch it with all DLC, and if possible a PS4 bundle could sell very well. The PS4's installbase will be well over 40million by the time RotTR launches on PS4.
I agree that when ROTR does release on PS4 it needs to be with all the DLC and maybe cheaper as well. However, that won't change the fact that game will be a year old and there will be many other new games releasing during that period. Hell, it's possible that ROTR on PS4 might have to go up against Horizon: Zero. Dawn.