I bought Xiaomi's because they were popular for custom ROMs, and their popularity was based on decent hardware for a decent price with a boot loader that's unlockable without too much hassle.
Once the bootloader unlock becomes a hassle, fewer developers will want to touch them, so their popularity for hobbyists will decline, therefore their sales will decline, leading to even further decreasing popularity amongst developers.
It'll be interesting to see how much difference it makes to sales, but Xiaomi will no longer be a preferred brand for me to consider. Pixels seem to be great for custom ROM compatibility, but they're ridiculously expensive even on the second hand market. Motorola might be the new go-to.