@Shatts When I mentioned 8-8.5 years, I meant in terms of the length of time between Switch's release and Switch successor's release. I fully expect the Switch itself to still be produced after the successor releases. Probably until around 2027 or 2028 depending on if the successor is backwards compatible and successful. I imagine evergreen titles would still be sold long after 2028 as well.
For what it's worth, all of those similar named successors sold less for specific reasons which could potentially be avoided this time.
SNES: Increased competition from SEGA (as well as Nintendo themselves with Game Boy, honestly). It doesn't look like we will get any new major players in the market in the coming years.
GBA: Legs cut short (likely due to competition from PSP).
3DS: Name, price, launch lineup and competition from mobile.
Wii U: Name, marketing, price, lineup and having trouble juggling two systems (3DS & Wii U).
