Not many countries have reliable broadband connections to allow gaming being solely via streaming. Also people in these countries do buy consoles and games now. Why lose all those customers? Why restrict people's choice and lessen your market?
It is also suggested that even in the US broadband is not always and everywhere reliable. I guess it is a risky step to be made. See all the reaction towards the always online DRM. People do not seem willing (or at least ready yet) to be completely internet dependent regarding their gaming hobby.
So, even if we cannot know what lies in the future, my estimation is that there will be a PS5 (or whatever) and 9th gen in general.

This, I stole from grandpa...It's called soap.







