Oh, yes, that would make sense. Hmm...I think he's too old to play Voldie's dad in the flashback scene. Fenrir is a possibility still. He couldn't be a Weasley, he'd look all wrong with red hair (I'd love to see Jason F. or Tony C. in there but it won't happen). And I just don't see him as Slughorn.

Oh, hang on! Maybe he's the new Minister of Magic!