It won't. You can't have a free app feature in-app purchases. It'll probably be around 99c, though, which doesn't bug me at all.
I hope if there is going to be a price on it they won't put ads in it, although I doubt it since Tapulous makes most of its money from the ads. Also is the minimum price for in app purchases 99¢? Since I'm happy to pay money for more songs, just not 99¢ per song.
I hope they get rid of the point system that gives different points for how accurate your hits are. I don't feel this ever worked as the performance issues with older devices really make it impossible to get good scores.
This game was announced a while ago. It was supposed to come out in July, according to pocketgamer,but I guess they delayed it http://www.pocketgamer.co.uk/r/iPhone/Tap+Tap+Revenge+3/news.asp?c=13825 anyway I'm excited for this game but I hope the in app purchases aren't that expensive
99 cents per song isn't bad I'd gladly pay that much for great or difficult songs. I buy a LOT of rockband songs which usually are $2.00.