Heh, this is nothing, Versus XIII will sell at least 8M if:
1- It remains exclusive (The hype will be massive if that happens, specialy if it's graphics are similar to Uncharted 2 or God of War III)
2- It's shown at E3 during Sony's conference with mindblowing gameplay and graphics! (Like uncharted 2 @ E3 :P)
3- Sony advertises it as if it was FFVII on the PS1
4- It is bundled with Special PS3s (like the lightning PS3 slim!)
5- It releases on Black Friday (World-Wide simultaneous release!)
6- It has better reviews than FFXIII
7- It is renamed "Final Fantasy XV"
You wait and see!