Well, the FFXV interest also comes from people who had little interest in the franchise...like me. Even though I have never really played a whole FF game and never felt interested to with FF Type 0 and FF XV, both games that I truly want, my interest in the franchise has awoken.
Still 10 million seems difficult but if the game receives genuine praise I can see it do 7 million retail. Depending on sales and digital it may do even better
Stories unfolded with my home made rap songs. Feel free to listen here with lyrics: https://youtu.be/vyT9PbK5_T0