Switch: 4.35M

PS4: 1.35M

I'm pretty sure the Switch'es baseline will be several K above last year, pretty much not dropping below 40K and half the time selling above 50K, with Pokemon giving a similar boost to holiday sales (less high, but spread over more weeks) as did Smash.

For the PS4, I fear the baseline will drop further and a steep drop incoming 1-2 weeks after KH3 release. PS4 won't get nearly the same boost with KH3 as it got last year with MHW and an even lower baseline means the lines spread out more and more.

Here's the summary for this thread. Predictions that were longer than two decimals were mathematically rounded to two. For people who gave ranges, the middle of the range was fed into the average. For people who gave multiple predictions based on certain conditions being fulfilled, the predictions that had more of the listed conditions fulfilled were used. Empty cells mean that the predictor in question omitted one of the two consoles.

The bolded numbers at the bottom are the averages, so 4.27m for Switch and 1.43m for the PS4. The final tallies in a couple of weeks will see the average Switch prediction being too low by only a few percent while the margin of error for the PS4 will almost certainly exceed 25%. Only one PS4 prediction in this thread will have been lower than the actual result, so too much optimism across the board.

EDIT: Added another column for the ratio by which Switch was predicted to outsell the PS4 (a 3.03:1 ratio on average).

Partly right, partly wrong. Switch does have a negative effect on PS4 sales, but it's not because Switch is seen as the successor to the PS4.

If we look at multiple generations, we can see that the PS handheld has cut into PS home console sales because many PS2 developers moved on to the PSP, so the PS3 took a significant hit at the level below AAA software. The progression of gamers here is PSP to PSV/3DS to Switch, rather than PSP to PSV to PS4 after Sony's exit from the handheld market. It's the Vita owners who have to go somewhere and they aren't sticking with the PS brand, so the PS4 can't benefit. Neither will the PS5.

Read over your second paragraph again because it's contradictory. You say that Switch is seen as successor to the PS4 and then pose the question why not get a Switch instead. The latter part implies that such gamers do not own a PS4 yet, so talking about a perceived successor doesn't make sense.