Considering they've only got one actor confirmed for the OOTP movie (Daniel Radcliffe - Harry) which is due to start filming around February next year (I think...), I'd say it'd be a while before we hear anything about casting for the HBP movie. Remember - most (if not, all) of the actors only had a 4-movie contract, meaning that there's a very high chance that not all of them are going to return for movies 5-7 and may be replaced by lookalikes or such.
Neverless, I really hope they'll have as many of the original actors as possible!
__________________ "You did your best and failed. The moral is 'never try'" - Homer Simpson
i know, i keep realising that and thinking AAAAHHH!!
and then I start to hope that JKR's gonna do some more books after the 7th one about what his job was like, or the first seven again from someone else's point of view, but she's blatently denied that already loads of times, so we'll just have to re-read the first 7.
really crazy btw, that they've got a release date for THBP, when we havn't even got a book yet, but I suppose they're just trying to keep some sort of schedule.
__________________ "Shame about the French, really. Obsessed with raisins. Humiliated grapes, really. Think about it."
- Captain Jack Sparrow