Yes, I think Jude Law would be a good choice. Orlando Bloom also springs to mind. I also liked Timothy Dalton in the Vanessa Redgrave film.
As for Elizabeth I, I'm not sure. How about Catherine McCormack who played her briefly but rather well in a UK drama "Gunpowder, Treason and Plot"?
I'm wondering whether this film will actually get made. I hope it does but fear it won't. Scarlett's people might decide that what with the Boleyn Girl she risks overdosing on period dramas. At the very least they may wait and see how the Boleyn Girl does before going ahead with MQoS.