At this point in time what do you think the lifetime sales totals of the 9th generation of consoles will be? My guesses are...

Nintendo Switch - 161 million 

PlayStation 5 -110 million

Xbox Series X/S- 47 million 

My prediction is:

Switch: 160M

PS5: 115M

XBSX: 45M

Switch 156m
PS5 119m
Xbox series 47m

Switch: 157M

PS5:128M

XBSX: 42M

The current gen is the most useless, almost no exclusive great AAA games for it. I brought Series S/X and PS5 and I couldn't be any more less enthusiastic about them.
I would be surprised if PS5 reach 110 mil, especially in the light of PS5 Pro. I think 100 mil is optimistic.

I can agree with this point somewhat, but I think that the gen will last longer than usually. Mostly because the rate of high profile game releases gets lower.  

Switch: 163M
PS5: 108M
XBO: 44M

Switch: 158m (Phased out quickly after replacement like PS4/DS)

PS5: 125m (Sells better than PS4 due to defecting Xbox users, but it's higher cost does limit it somewhat)

XBS: 39m (Now that its games are coming to PS5, its sales peter out)

By 2027 the PS5 is at risk of being just as fast as an AMD APU (and I don't mean the Strix Halo which should come late this year/early next year and already beat the PS5), meaning 720p-1080p low would be standard PS5 settings by then. On a big TV that lack of visual fidelity will be absolutely visible.

Switch can get away with those things due to being a handheld system (and even then it has it's limits, Mortal Kombat 1, anyone?), but a console whose entire premise is it's graphical prowess? I seriously doubt that.

PS5 = <90M
Series = <40M
Switch = ~152M