I understand your worries, but there's nothing that can't be fixed.
Options, as I see them:
-order the MSI board before Christmas, check the serial and if too old, return the board;
-order an ASUS board with Flashback, check the BIOS version and if update needed, use Flashback;
-cancel the order for 4690k (if possible) and order a CPU that doesn't require a BIOS update.