OOTP is more of a reflective book, looking at questions being answered, not like the action packed GOF, so i agree that it wouldnt be altered that greatly, but i think they would (as always) only include the vital information. Parts like the christmas at 12 Grimmauld place would probably only be really short, and i dont think the part about lockhart in st mungos would be included, because its not really necessary. Even though in the part with Lockhart the trio see the man who got strangled by the plant, the director would probably only make the trio walk past his room while getting to arthur's bed.