A website has revealed the codes to gain the Unova starters with their hidden abilities.
The codes probably only work in the japanese version (unfortunately confirmed), but there isn't anything stopping us from playing the games in japanese to redeem them!
All of the codes have been officially revealed now.
Contrary Serperior
POKEMON497
Reckless Emboar
POKEMON500
Shell Armor Samurott
POKEMON503
I don't know about the other two, but the code for Serperior can't be redeemed until January 9th.
The codes for Emboar and Samurott can't be redeemd until January 16th.