It will most likely be on 10.3 if you buy it new.
Confirmed on Amazon.de
My Hyrule Warrior edition which is quite recent was on 10.3.
By looking at the comment:
"Als Firmware war bei mir 10.3 installiert."
Yes, here is the link if you want to check yourself:
https://www.amazon.de/gp/customer-reviews/R2RCMXU7SGI0UW/