'Primary storage'
So basically the same as we've had for a while now, SSD for the boot/system device and HDD for cheap bulk storage?
Sooner or later SSD will be cheap enough to use for everything but for the D: bulk cold store for all the junk had still has a role.
I do wonder though how many people know the difference between a cheap commodity SSD with low life & IOPS and a decent high grade NVMe one? A lot of the cheap stuff is slow garbage.