Unsurprisingly, there's even a few hacks out there for upgrading old C64s with newer/better components, too, if you want to get another couple decades out of it. There's even new manufacture C64-compatible enthusiast boards being produced [1], although I believe you may have to supply your own SID chip. The latter doesn't count much for this topic, but it illustrates there's some interest. Further, the parts that are likely to break over time are fairly trivial for someone with soldering skills to replace. I know of at least a couple people who preemptively replaced capacitors on old C64s they bought and refurbished.

[1] https://icomp.de/shop-icomp/en/produkt-details/product/c64-r...

I wouldn't put money on that. A C64's starting price was $600 in 1982 dollars. For $154 in 1982, quite a few people might have been willing.

That was pretty much expected. Hardware upgrades were just as fast and furious as they are now, if not moreso. Backwards compatibility with years-old systems at the consumer level was a byproduct, not a plan.