Hyrule Warriors Legends on 3DS shows why PS4.5 might not be a good idea.

[Soundwave]

The New 3DS -- 3DS jump isn't even that big. A 20% difference maybe. PS4.5 is a monstrous leap in GPU performance, from 1.8 TFLOP to over 4 TFLOP.

If you can notice a difference between the XBox One at 1.2 TLFOP and PS4 at 1.8 TFLOP ... lol, you will notice the difference with the PS4.5.