The main problem you’ll have is that you’ll want to upgrade archlinux-keyring first. Beyond that, it wouldn’t surprise me at all, though it also wouldn’t surpri

The main problem you’ll have is that you’ll want to upgrade archlinux-keyring first. Beyond that, it wouldn’t surprise me at all, though it also wouldn’t surprise me if you did have problems. Early last year I updated a machine I hadn’t booted for 2½ years, and I messed up the procedure a bit and ended up rendering it unbootable (the way I did it, upgrades in the pacman hooks system meant they didn’t run properly, so mkinitcpio didn’t happen, so I couldn’t boot past grub), but when I came back to that machine almost a year later and fixed it up by booting from USB, chrooting into the local installation and I think just reinstalling the linux package as a convenient way to trigger the mkinitcpio hooks, then it was fine, and after just a manual archlinux-keyring update the year’s worth of updates were uneventful. (I think if I’d tried to do the whole three years’ worth in one go it might have failed, though, vague recollections of the .tar.xz transition or something.)