I was waiting for confirmation before posting this and now we have it! Domhnall Gleeson (son of Brendan Gleeson who plays Mad-Eye Moody) has been cast as Bill Weasley in Harry Potter and the Deathly Hallows.

Dear UHP Staff.
Domhnall Gleeson is attached to the forthcoming Harry Potter movie.
He will be playing the role of Bill Weasley.
Best regards,
Eva Klos

Thanks UHP