PS5 not beating PS4 is very possible, but even so, numbers still point at +110m consoles.
There are too many factors to consider here, to name a few:
The 2 consoles, PS5 and PS4, are too damn close in sales, i don't think ps4 will lead by +8M.
PS5 still has no price cut.
PS5 faced gigantic shortage due to COVID early in the gen.
PS5 has unprecedented number o crossgen titles with PS4. Many users are waiting to make upgrade. GTA VI, future PS exclusives and other games are going to fix this.
Xbox is likely becoming a 3°party, many gamers will making the jump to PS5.
I think+110M and under 130M is a safe bet.