"planning half a decade or more into the future with a tech purchase often doesn't pan out that way, at least from my experience." This is a more relevant statement for PC / Windows end of things, perhaps general tech, where things depreciate quickly, but Macs are different. Back in 2012 - I had an option of retaining unibodies with various configurations - all seemingly powerful then, vs. investing into a maxed-out MBA, with a new architecture on I7 intel and 8gigs of ram vs standard 2 or 4. Fast forward to now, and that maxed out MBA (which i bought as a refurb from Apple with an extra discount) is still relevant today, works for me as a daily driver just fine (well, beginning to show its limitations). So, have I chosen not to opt for higher capacities then, I'd be faced with a necessity to upgrade much sooner, maybe a few times, which, in the end, would be just money wasted, and lots of it. Was the maxed-out MBA pricier than the regular ones by some crazy factor? Yes, but buying new ones along the way would still be more expensive in the end.
Besides, is getting 16 gigs of ram today an act of future-proofing, or is it more like present-proofing? Have you considered the complexities of simple photos taken with a modern iPhone and then transferred to a Mac? Features like Live view and HDR, videos in 4K? And that's just one example. As long as Apple keeps telling us how much ram is on board it will signify that the metric is relevant and I'd always look to buy the highest capacity I can, as upgrading later by selling and buying new will burn more money and time. While A LOT depends on the individual's needs and uses, I'd say that back in 2012 i had no idea id need my Mac to cut videos with Final Cut - so I am very happy I spent extra on a machine that could handle it.
