This will hit #1. It's Top 100 on iTunes without adds date, much pre-adds date radio support, discount, remix, etc. It's still got plenty of time to smash. The video has done wonders for thi song! (well, the exposure of it... the song itself is what's making people buy it because it's flawless).
EDIT: BTW this song is what made Katy Perry my second fave over another pop star, who is now my third fave. It's also my favourite Katy single and song ever.