The Attack on Titan game could do pretty decent as well.
Well uh... no ?
Seeing how fast the game is being released it's probably a low budget effort, and it's not because the anime is selling pretty well that a game based on it will be million-seller or something.
You can look at the Madoka's game to have an idea of how much it will sell, and as mentionned above it will be a Visual Novel so it'll more likely end up selling less than that