Here we are again. I mean I am the only one that remembers people predicting the Wii would maybe do better than the Ps2, that the Ps4 wouldn't pass the 100 million, that the Switch would fail, that the PsP/DS would be a tight race. Many of those predictions were done many months or even years after the launch. So sorry but I don't think that anyone can actually really know how many Switch or PS5 are going to be sold.
I don't ever remember anyone saying that PS4 wouldn't clear 100 million, if anything all of the early guesstimates were that it would surpass PS2 numbers. As for Switch, I think the PS5 and Series X hardware droughts are only going to make it reach new heights in their yearly install base.