I think it will deffo be Top 10. I agree with what others say though, if this goes #1 it's purely because it's Katy. The song itself doesn't scream #1 to me personally, compared to the likes of "Firework".
It will go either way, the GP will eat it up and it will go #1. Or they won't and it'll still be #10 due to Katy's single numbers.