Like you said yourself even the Xbone despite the controversy that haunted it at the time sold more than the Switch in its first two months, so its very hard to imagine a scenario where both of the new consoles don't do the same.

If you want specific predictions I'll say:
PS5 - 5,6 mil (assuming it launches in Japan right away unlike the PS4)
Series X - 3,7 mil

Yes launch aligned Switch have sold more than PS4, but not in any way similar to the difference of switch launch window+holidays versus PS4 launch + first march and april. And again if there was more inventory PS4 and Switch would have sold more on launch, showing that for launch it being on holiday doesn't necessarily improve sales that much.

It is beneficial to launch as early as possible, if holiday would be so much better then why didn't Nintendo wait for Holiday in 2017 to launch? Sony had released outside of holiday in the past. And you can bet that if Nintendo could have launched on Holiday 2016 they would have, but that is because they would like to launch earlier than later.

If inventory is there both can possibly outsell it.

Well, the PS5 should take this. Switch is no competition, if you look at the PS4-Switch launch aligned comparison, it is easy to see how the PS4 can pull ahead with a holiday launch. Switch comes back as it itself enters holiday and they started dancing around each other at their respective holidays until recently. So the holiday-launch of PS5 will surely push it past Switch. The XBSX will probably also be ahead of Switch, because of the holidays, but lag behind PS5 because of Japan.

The price, simple as that.

I think right now, with the Corona Virus and all that. People are not going to be able to spend as much (at least part of the target population).
Maybe they will surprise us with the price and then I will def. adjust this way up. 

I do not agree with the "weak launch lineup" for the Switch.
Zelda WAS a console seller and I could not say the same about any game coming out for the 2 next gens.

The games you are mentioning are ALL available on current gens. This is a very different story.

While I am actually looking forward to play those games on my Series X, I do not need it and nobody will need to buy a next gen console to play them. Zelda, was a Switch game, for the Switch. And it moved a LOT of console :)

In the first two months it will be depending more from supply than from demand.

All three companies should have a few million hardcore fans / eary adopters.

But... Zelda was a Wii U game too. No one needed to buy a Switch to play it either.

Hum... True, I thought the WiiU version did not sell as near as the Switch one (esp. in the first few months and it was pretty abysmal)?
Honestly, that is what I recall at least (Did not check any numbers today) :) So if this was not the case, then yah maybe calling it a console seller may be a stretch but at the same time, it really had a huge impact which none of the launch titles on the 2 next gens will have imo.

I feel like this is more about inventory than anything else. Will stock be able to keep up with demand in the first 2 months? That seems like the limiting factor for those early sales more than anything else for most recent console launches.

Are we comparing launch periods (IE. first 2 - 3 months) or just the launch week?

Either way, PS5 is going to crush all sorts of records when it launches, I wouldn't be surprised if Sony moved 3 - 4 Million PS5's on launch week if they had enough supply to meet demand. Series X has a slight chance to outsell the Switch too because its launching during the holidays.