In a new interview with actor Timothy Spall, Spall confirms that he will be making an appearance in the last two Harry Potter movies, Half-Blood Prince and Deathly Hallows
Well I'm actually.... yes... I'm in the next one. And I'm also in the one at the end - I have a very big scene in that. I think they might be shooting two of them back-to-back - hard to know though, what with this writer's strike and all. They're shooting the penultimate one at the moment - which I have a brief appearance in it. I should be doing that soon.