According to The Numbers, Britney's 2nd role as Drew Heart in the comedy "In The Pink" with Cher, Bette Midler and Tim Allen is set to gross $45,964,454 in the US, this would top Britney's first role in "Crossroads" which grossed $37,188,667. The movie is set to begin filming in 2006.
Note that this is still un-official information. Bette Midler confirmed a few months ago she didn't plan to be a part of the cast and that she didn't think she'd ever work with Britney. She concluded saying there was no such project happening.