Why future-proof your board when your CPU will limit you sooner?
I think there's no point obsessing over your motherboard's longevity besides making sure it has strong VRMs, features you'll realistically need today or within the next year, and enough room for one drop-in upgrade. Beyond that point, you're just paying for theoretical value that you may never even benefit from. That's especially true for gaming PCs, where the CPU and GPU usually determine when your build starts feeling outdated, not the motherboard itself. Sure, if you're an early adopter, splurge on a high-end board by all means if you're willing to stick with the platform, but for everyone
Should BIOS chip capacity affect your purchase decisions?
From a future-proofing standpoint, it is well worth a consideration. If you are planning to upgrade your CPU down the line, or perhaps reuse the board with an older processor for another reserved build, a higher-capacity chip reduces the risk of losing backwards compatibility when new BIOS versions arrive. It is also important to note that smaller chips can also compel manufacturers to cut conveniences like on-board Wi-Fi drivers (as manufacturers like ASUS state) to free up space. Cost is also a noteworthy consideration, but for longevity-minded builders, it's worth prioritizing.