The console wars thrive on sore losers and the outcome of the eighth generation hasn't been beneficial for warfare. You'll remember the seventh generation as a lot more intense because Sony was on the losing side and their fanbase has the most trouble to come to grips with defeats. The Nintendo and Xbox camps are more acceptant of lows in the business, so there isn't prolonged resistance to reality. Compare that to the seventh generation where you still have Sony fans to this day who have a hard time to admit that the Wii won and instead come up with reasons how it didn't.
The same reality distortion blends out how it wasn't all sunshine and roses for Sony in the eighth generation. While the PS4 dominated in the home console space, Sony suffered a crushing defeat in the handheld market and made an exit. But eventually the consequences will be realized and people will begin to recognize that the PS5 won't be able to win like the PS4, let alone dominate. When the PS5 launches and starts with an installed base from scratch while Switch has a lead of ~60m units, then launch-aligned comparisons will make people realize that the PS5 has to sell better than the PS4 to even have a shot at beating Switch and winning the generation. Then you have the people who believe that Switch is eighth gen, but for them the problem will be that the PS4's win is in question. So regardless of which generation Switch is put in, Sony fans will have to explain away Nintendo's success and the console wars will be back. We've gone through a long phase of "Switch sales will decline soon, so it will be no threat to Sony's numbers", but with each passing month those people must be getting more worried.
There's also still Microsoft left who can add more spice to the whole thing. A stronger performing Xbox cuts into PS sales, I think that's clear to everyone. Right now is the calm before the storm, but the ninth generation will provide a dramatic shift because we already know a lot about Switch and there can't be an easy win for PS like in the eighth generation.
As for the OP's closing question, the state of VGC is so dire that intense console wars are absolutely needed. More activity means more people, and more people offers the chance that more discussions outside of console wars are created.
Dont count on it.
MS has made it clear that Stadia will be their major enemy and that is because Stadia is doing what MS has wanted to do all along. Those studio's MS acquired were not to bloster strength against Sony, but to ensure enough content for the fight for "games as a service" war. MS could care less about winning the console wars and the only reason they're going with another one is just to keep fans on board to help win that fight.
I definitely think you are underestimating Sony. They will not start from scratch. Sony is making moves that ensure all those useres who loved PS4 or PS in general will have hard time not choosing PS5. PS5 is looking to be very similar to Wii U and Switch where Switch literally ate the Wii U and just built on top of it but in PS5's case its not just tech, but user stats: trophies, games, save data, , PS store, Ps now ext. If you gamed heavily on PS4 why would you not choose PS5? You start where you left off.