All the guys with preview units said they never want to go back to not having it
To me this isn't for playing a ton of huge single player games at once, but great for having like your main RPG loaded up, then easily switch to a sports or more chill game when you want a change of pace and then easily hop back into your RPG without all the loading screens the next time you play. It's gonna be one of those we'll laugh about not having in prior generations
PS5 should have the capability for this as well with its SSD but Sony been mighty coy about it