@alexia I think it will be feasible. Hopefully applications won't require 8GB of memory just to function in the future. That would be absurd.
My main concern is the availability of battery replacements. It would make it much easier if there was a battery size and connection standard in the future. But since all phones are different shapes and sizes that wouldn't work.
The Fairphone is probably the best in terms of what we want. But it's a lot of money and isn't available to purchase from my country. The PinePhone also uses a J7 sized battery which can still be found on ebay. But the device isn't made to last.