Better late than never... There is a review
of Mythologies on Game Informer
. Within this preview Game Informer states that, "We believe that Sub-Zero's ultimate goal is to obtain the Lost Amulet from the new Mortal Kombat bad-boy, Shinnok, who is also the last boss in MK4."
Whoa, now doesn't that sound familiar? They also mention, "Look for this title on the PlayStation this September, with the N64 version following in October."
So it seems like that answers the mystery release dates