I definitely am of the same position as you here. The question is whether the Switch is a successor to the WiiU or the DS.
I think Switch continues the legacy of Nintendos portable machines, not the failures of their home consoles (apart from Wii). The Switch lite really solidified this view for me.
Xbox is basically on the death walk.... so PS will possibly be the only home console option and the closest competition I see for them is PC / Steam, with steamdeck and possibly more console like boxes on the way...
I think Switch is intended to be the successor of both WiiU and DS, plus Wii, 3DS, PSP and Vita.
I think the part of being the successor of PSP and Vita, as "the only powerful portable device of the generation capable of running current gen indies and almost some big 3rd party home console like games", has been very important too.
This last part Switch 2 won't enjoy it anymore because PC handhelds will steal it, since unlike Nintendo they'll have access to almost all the entire PC catalog with 1:1 quality, only not with high end visuals for the high end games. It represents a small part of Switch business/game sales, which I think will be reduced and will make Nintendo lose a small part of their market share.
So I think Nintendo will continue focusing, maybe even more, on their own exclusives and their own device in the medium term with Switch 2. But Sony will be highly growing in all areas specially once (MS made, not PC handheld) Xbox hardware dissapears getting all the Xbox market share, and being more powerful in all areas I think will also steal a small part of Nintendo's share (specially when Sony opens their PC PSN store and makes it available to the PC handhelds).
And well, mobile continues being the biggest and fastest growing market in the last several years, plus now it's starting to get AAA games natively and via cloud gaming, which will continue improving, plus all the main console/PC big publishers are bringing their IPs to mobile. So I think mobile will also steal a bit of Nintendo's market share.
So I think "Switch 3" (or who knows if Switch 2, I think it's unlikely) may be the last Nintendo console as we understand them today, with dedicated OS and exclusive games.
I think at that point, the hardware similarity, catalog similarity, game engines evolution, multiple stores available almost everywhere pretty likely with crossbuy, cloud gaming, evolution of PC handhelds and home console shaped PCs will finally unite console+pc+mobile into a single unified gaming market where you'll be able to buy your games and play them in any device independently of the device type or hardware brand.
Regarding Sony, I think during PS6 all their games will be on PC and cloud day one and some in mobile too. The PS Player successor will continue being sold as PS6 accesory but also as PC handheld to run there the Sony PC PSN games natively + cloud gaming + remote play, and I think will become the best selling PC handheld.
I think it will be the start of a crossplatform PSN: buy your game once and play it in PS console, PC, PC handheld, mobile or smart tv. I think multiplatform stores from different brands (MS, Sony, Apple, Google, Epic, Valve, EA, Ubi, Take 2...) will start to compete, converging even more the console, PC, mobile and cloud markets.
I think the store and their catalog and your library there will be more important than the device where you play them. This also will make Sony, MS, Nintendo, etc. to take bigger efforts in BC (specially for digital games) to give more reasons to people to join their platforms.
In PS7 I think all their games will also be day one on mobile and probably -even if their hardware and OS already have been mostly PCs since the previous generation-, they'll be open to allow "other OS" in PS7 as in PS3 or as in the PC handhelds to also feature the rest of stores and emulators, because basically everybody else (except Nintendo) will already have them and in comparision would be perceived as something many people may mention to don't have bought a PS6 to play.
So by 2034, around 10 years from now, I think we'll start to be in a total multiplatform gaming market. You'll be able to play all your PS1-PS7 games natively or via cloud on your "PSP4", a tablet, phone, PC or PSVR4 buying them only once instead of separatedly for each device. Plus also having the emulators, games from MS or Nintendo, mobile, PC, etc. on the PS7, "PSP4" and "PSVR4".