It's one iterative console. Not iterative consoles in every gen forever. It's one iterative console to bridge the gap between gens due to 4K becoming more mainstream and to support the purchasing of those sets and the consumption of 4K content. All of which carries a higher price, lower likelihood of steaming and, for media companies, hopefully slow or reverse cord cutting. There's zero evidence or rationale at all for iterative consoles forever.
Which is already happening.
These doomsday scenarios have no basis at all in reality or even in rumor from the development community that actually knows what is going on.
But that would point towards a more media focused 4K Ps4 with no real need for more power to games. You'd have some updates to the GPU to support decode of 4K blurays, HDMI 2.0 and a UHD drive, but none of that needs to impact game development