Somewhat scary. I have several Linux virtual machines that I only use every couple months (they're running Debian, though). If you don't upgrade in time, is your system hosed? Or will Arch provide some way to upgrade to 5.0.1 after that date?
I would say in that case you could probably run 'pacman -S pacman' to just update pacman and then 'pacman -Syu' to update the entire system after that
Besides VMs, there are also single board computers. Not sure if this limitation also applies to ArchLinuxARM as well, so better find the ArchLinux system images I have sitting around on SD Cards (used with RPi mostly) that I haven't run recently (running them for different projects) and better upgrade them.