No, we are clearly told that the Qura'an will never change.
BUT the same have not been said about the other books. We have also been told we cannot believe OR disbelieve anything in the other holy books because we don't know what is the truth and what is not the truth in them. But overall, they are the predecessors to the Qura'an and we should work by what the Qura'an tells us.
Moreover, when the Qura'an came, it overruled the other books. Therefore, you should abide by the rules of the Qura'an and not any other book. Nevertheless, you MUST respect the other books.
Think about it like rules and regulations in airports: 20 years ago you were allowed to take liquids and a number of other things on to the plane. Now you have so many more restrictions.
That does not mean the old law was changed that is why we dont believe it. It just means the previous regulations are not sufficient for today and we have to abide by new ones (This does not mean I agree or disagree with either of these laws of airport).