The big question is if they can manage to get day 1 COD2024 as launch title/window. That + Assasins Creed Red (that is based in Japan so I think a SKU for a Nintendo system can be a good addition.) can be a very good start for Switch NG regarding (western) third party support.
Like a (fall) launch with (only considering NG exclusive games):
1) 3D Mario (Nintendo)
2) 2024COD (Activision-Blizzard)
3) Assasins Creed Red (Ubisoft)
4) Avatar: Frontiers of Pandora (Ubisoft)
5) Madden/FIFA/NHL/UFC (EA)
6) NBA 2k (Take-2)
7) Something from Capcom (DD2?)
8) Something from Konami (MGS3D?)
9) Something from Square-Enix (FFXV?)
10) Something from Bandai-Namco (Tekken 8?)
11) Something from Rockstar (RDR2?)
+ update to existing Switch 1 titles.
So I think that Nintendo will make a “soft” launch and not releasing every mayor AAA PS4/5 day 1.
I think people are overestimating the capabilities and impact of the device.
The difference between PS5/XXS and NX2 should be roughly similar to the difference between PS4/XOne and Switch.
Very few last-gen games came to Switch, most of which would certainly be possible.
I do believe anything is possible with enough effort but storage and online will probably still be major pains.
Also, it will take years for NX2 user base to grow.
Any AAA 3rd-party title releasing in the first year will sell to a initially tiny audience.
If there are a handful of those, they will dilute each others sales.
They could have a long tail in sales, but I believe any hype when the release would quickly dry up as new games come out.
And Nintendo games always sell better.
Technically, anything is possible, but most ports may not be worth the investment at all.
There will be a few ports. Nintendo should be financing a couple themselves.
But I believe most 3rd-parties will first observe as things evolve before committing to anything.