It's not upscaling but rendering in 4K. Which definitely needs an upgraded GPU.
But that suggests a much bigger GPU upgrade, has a knock on effect on RAM, and games need to be specifically written or patched to render in 4K. So you create a two tier system. Also, if you have the GPU and RAM for 4K rendering, why cant devs use that power to create a better 1080p experience? 900p30 on PS4, 1080p60 or 4k30 on PS4.5?
Now I'm fine with this as part of an ongoing iteration cycle and stepping stone to PS5. But to be worthwhile PS5 needs to be a little further away than we first thought, closer to 2021 than 2019. Otherwise why not just jump in with a PS5 in the 2018 timescale?
The ongoing R&D required for that kind of GPU jump means this has been in the works for a very long time. Which again leads to a .5 step and moving to console iterations.
It's seems to be that different parts of the rumor contradict themselves.
Also question the value in releasing a machine that renders 4K in the 2016/7 time frame. Upscalling, yes, rendering - a lot of expense for a small target market. For rendering a PS5 in the 2018/9 when TVs are more embedded in peoples homes makes more sense.