Well, yeah ... but that's a different market.
As it is, I think it's probably much better to split this one up. There's a natural break: end the first one after Ron returns and destroys the locket; and then pick up with the rest of the book. You'd get two good movies, and there'd be space for all ot the details that would otherwise have to be worked around.
In fact, that chapter from Deathly Hallows ("The Silver Doe") is a very important climax for what amounts to the first storytelling arc in the novel. Once we go to the next chapter ("Xenophilius Lovegood"), the second storytelling arc involving the Deathly Hallows starts up.
How so? They're both fantasy books that draw to a largely teenage crowd, with its share of older fans.