Unless you configure pihole to connect to CF via DoH, the above is still entirely true. Pihole is not a privacy tool, it’s a filtering tool.
I used to have this setup too until I realised spending a single hour per year on pihole “costs” me more than paying for a good DNS resolver which can also do the blocking, and I can easily use on my phone as well when I’m away. I’m very happy to have switched, personally.
Very difficult to predict the future, but my bet would be on no (to the in 20years question).
I doubt the hardware would last 20 years and eventually it’ll become hard to source parts as the popularity falls off, even if you could repair it yourself. I’m sure anything with an online dependency will not work either, but offline games have a chance.
But the real question is would you want to use the switch in 20 years (or honestly, even today)? There is already a better alternative (steam deck) with a much more open platform with way more capabilities and I believe it can already emulate Nintendo games (although no first hand experience with that)
I have a switch myself and would never recommend it to anyone personally.