I think it might drop to #15ish on iTunes towards the end of the week, but no further, and then return to the top 10 for the second week.
I'm saying #15 - #20 first week if it's sales and airplay alone (without a heavy radio deal). It they put the video out with the song and have a good deal I'd say top 5 first week easily.
I don't actually care all that much though, I'm just glad she's back again with the enthusiasm we've all missed
