Ristolainen has played average game against other juniors. He is very impressive for someone his age but since he doesn't really stand out in juniors, you can't expect him to play in WJC.
Määttä has played fairly well against men in second highest level in Finland. That is something too few of our defenders have accomplished. But still I doubt that he is so good that he should play this young in WJC.
Anyway it seems that there are few promising prospects in 94's. Määttä, Ristolainen and Ville Pokka seems to be very good for someone their age.