Clemence Poesy, who played Fleur Delacour in Harry Potter and the Goblet of Fire, will most likely be returning for Deathly Hallows.  Thanks to UHP who got this bit of information from her representation:

Clemence Poesy is strongly predicted to play Fleur Delacour in Harry Potter and the Deathly Hallows, but it hasn’t been confirmed yet. (But) it is strongly suggested that she will come back to play this role.

This is NOT confirmed but hopefully it is true.