I had a feeling this would happen, and it's quite fitting.
The moment Pixar starts selling out (meaning, making movies to make money in merchandise sales instead of making movies to make something really worthwhile to watch), it is going to hurt their name. Disney should have already learned from their mistake, but either way, the pencil pushers don't care, do they? They see huge merchandise sales and don't feel like they need to re-examine the way they do things.
Of all the Pixar properties, I have always felt that Cars has been the weakest link. All of the other films have that classic Disney heart, whereas Cars seems to be just an ok movie...something that I would have expected out of Disney after it's renaissance. But it is near and dear to John Lasseter's heart, one of his pet projects (inspired by a family road trip he took), and the man has a lot of power and freedom now to do mostly whatever he wants. Unfortunately, I think he's wearing rose-tinted glasses where Cars is concerned. We'll see how this pans out for Disney in the long run...it's not like other companies haven't run franchises into the ground and won't give up (Shrek being a perfect example).
Either way, little boys are always going to want their toy cars...and Disney knows it.