Games aren't "built" around HDD or SSD speeds at all, as far as I know - loading between levels takes whatever it takes, and in-game loading is not to my knowledge bottlenecked even by old 7200 RPM/SATA III HDDs. I think HDDs will still be prevalent enough in the next five years that there will be no games requiring an SSD.
Sony claims the PS5's SSD has higher "raw speed" than any existing PC-based SSD, but that is a meaningless claim. There are multiple methods to measure SSD speed (sequential, random, small file size, large file size, write speed, read speed, etc) that without hard evidence, I'm chalking their claim up to complete marketing fluff. They compare the speed to the PS4 Pro, but the PS4 Pro only has a standard spinning HDD... and it's 5400 RPM, not even today's modern 7200 RPM drives.
The point being, I am very doubtful that Sony has some secret sauce SSD in there - and even if it does, is the difference of, say, a 2 second load screen versus a 0.5 second load screen worth waiting to upgrade when you can get extremely good and extremely affordable SSDs right now? I say no - if you have a need for an SSD now, get it.
tl;dr: I don't think there's any special thing going on with Son'y SSD in the PS5. I could definitely be wrong, but it sounds a whole lot like marketing fluff so far, as the only comparison they've given us is one versus an old HDD.