Traditional generations are over people. Playstation 5 will come, but the majority of its games will also work on PS4 (with worse framerate and graphics). Microsoft will do the same, but because they can still lean on PC and xbox one x, they can afford to wait longer. They will never actually sell more consoles than Sony anyway, unless they shoot themselves in the foot a la PS3. And even then it was only 2 markets where 360 sold more, where PS3 did better rest of the world. Its all about maximizing profits, which is why Microsoft got in to PC again in the first place (biggest platform in the world by quite a huge margin).
I don't think generations are over. True, they will not be about gaphics anymore, but there will always be opprtunities for improvement. Nintendo's two best selling"home" consoles of this century were both about advancing gaming in other ways besides graphics.