That is so wrong, Vitalik will kill ETH switching to PoS, and GPU mining will stay for a very long time, remember that GPU can mine a lot of algos, and can be created new ones to mine. That is not the same reality to ASIC devices.
I know that GPUs can mine a lot of algos, I have over 100 of them. However, if you look at the hashing power on ETH as it disperses to other coins... the diff will be so high on those they won't be profitable. Vitalik will kill gpu mining. @Metroid will finally be correct.