Enterprise Linux distros such as RHEL regularly provide 10-12 years of support you can pay for per major version and presumably you will be able to upgrade the major version to reset the time.
Same thing for community Linux distros - Fedora, Debian of OpenSUSE already work on current 16+ years old hardware and one can expect that to continue in the future.
It's just a friend's kid's video player right now, because with OSX it's become too slow for most uses, but if someone put Linux or BSD on it....
Case in point, my ThinkPad T420 has been in use since 2011. Even though it's no longer my main driver, the performance is more than good enough for when I need a backup device.
For comparison, 16 years ago, we're talking about single-core 32-bit CPUs, the very first version of their Centrino brand, DDR2 RAM and IDE/PATA HDDs. There's just not much you can do with those limitations.
The human brain runs off umptillion neurons each running at 100-1000 Hz (depending on measure). Not GHz, MHz or even kHz. Hz. Obviously it's an extreme case, but if general intelligence can be achieved without fast serial computing then there should be lots of things we can do with a few dozen cores all running at GHz rates.
Right now we are hitting the threshold of incompetent programmers and tools long before any other.
I have a very lean setup on it with Linux. I don't think it'll last too much longer to be honest.
I mainly use it if I'm on my phone, but find something that a bigger screen/keyboard would help.
But I can't do much on it. Even a RPi has more RAM on it.