Switch line, yes. But the Switch 1 and its revisions will not reach 10 years.

And your post stumbles at the first point: after X2, there are no new Tegras out or in current development to our knowledge. The tech and personnel behind X1 and X2 are working on Xavier which is not at all designed for consumer electronics, much less a small tablet form factor

Xavier finished last year, and though it seems to be working perfectly fine for consumer electronics as well. Actual problem comes from Xavier's minimum configuration likely consuming at least four times as more power than Switch. With future Tegra project - Orin - expected to run even more power hungry and hotter.

Considering Nvidia's track record, I don't think they will even bother if Nintendo would request a very heavily customized based SoC...

Yes, it is. I expect this device to have about 5 years of commercial run, the brand will last for a longer time, though.

I was initially concerned about how the Switch would last given the fact it is another Nintendo console that is technically behind the other big 2 (yet again!). Whilst this doesn't really matter too much from a graphical perspective anymore (we haven't had a major graphical jump for years) it is a problem in that the major developers who make cross-console releases for PS and Xbox won't be able to fit their games on the Switch. They're struggling now apart from a few notable exceptions (Bethesda & Take Two in particular) so they definitely won't be able to port over new games from the next gen - at least not without major compromises.

However there is hope here. The Switch was never meant to go up against these 2 in a technical battle, it's here to supply the alternative gaming option and it's done a good job of that so far. The Switch's unique hybrid ability means it can work as their next full home console as a successor to the Wii U (this is how I believe most people see it) but it can also work as their follow up to the 3DS (how I think people will eventually see it). What I mean by this is when the next PS and Xbox come out in presumably late 2020 they will have launch prices of somewhere between £350-£450. The Switch will be a budget system at around £200 (hopefully even less) and will have a massive library by this point. A lot of people will still be buying the Switch as a cheaper portable console (I can't see Sony or Microsoft releasing a handheld for next gen). This isn't even factoring the hardware revisions Nintendo will bring out to boost its appeal (I'm thinking of an even more cost friendly "lite" version or a more powered "pro" version).

It's hard to predict but I think the Switch will last up to 2023/2024 as long as Nintendo can keep smashing it out the park with big hits and we are able to get more awesome exclusives from 3rd party developers (like Octopath Traveler & Mario + Rabbids).

In terms of total sales i'm going with an optimistic total of between 80-90 million.

Actually, Xavier - which I did not realized had launched- is used in 0 consumer electronics and is planned for 0.  It is designed for autonomous machines and self-driving cars.

Actually, I think a bespoke Nvidia chipset using tech developed in the making of Xavier and perhaps the next peoject is high likely for Switch 2.

X2 is an easy Switch Pro with modifications.  A bespoke will absolutely be necessary past that point.  

I think so, HH and Consoles are made to be relevant for at least 5 years.

I still think that in 2021-2022 there will be a Switch 2 to replace the first Switch, and to be able to keep up (getting 3rd party ports) from PS5/XB2.

A full on successor that early is unlikely.  A pro version makes more sense to sort of ride out the inevitable period of 8th to 9th gen cross gen games.  I think the earliest a Switch 2 could launch would be holiday 2022 but even that feels unlikely.  Early 2023 to holiday 2023 seems more likely.

Well, most consoles are designed to last from the manufacturers perspective, the real question is always whether or not it will once it hits the actual market and gains traction. It remains to be seen, it's still young, it had a great 2018, but we also need to remember when comparing to the 7th and 8th gen that Nintendo doesn't really have a dedicated handheld selling much at the moment. Without two parallel markets moving significant amounts of hardware, more load is put on the Switch's shoulders to carry overall sales.

I'm still not sure, I've said from before launch that I'm unsure of the longevity of the Switch due to its tablet-like design and marketing, as well as their insistence on holding back on, or even completely foregoing multimedia functionality, connectivity and app support and proper online infrastructures. I guess the most realistic answer is "we'll see", at least from where I'm sitting.

Nintendo would have rolled with the Wii for a decade as well if they could. It's up to the consumers how long the Switch will hold.