I'm not sure how I feel about this, I have always loved the BBC adaptations of the first 4 Narnia books, and I enjoyed the first film when I first saw it, however I wasn't very impressed wit the prince caspian film, and having since read the books for the first time I can see that they made a lot of changes, a few of the good and most of them bad, and when I saw TLTWATW again it struck me that although the adaptation was fairly faithful the dialogue had been modernised in a horrible way.
I agree with nOmArch that VofDT will not adapt very well to film, so I can see this going two ways either they'll make a lot of changes to make it into a more standard fantasy adventure film which means we'll get another horrible adaptation like Prince Caspian, or they'll make a very faithful adaptation which will probably be seen as boring by most and which I will never watch simply because of the association with Prince Caspian (which I don't want to watch again and although it could be improved by a fan-edit it can't be fixed), and after that they'll have to try and make an adaptation of Silver Chair which is probably even harder as it doesn't have a very serious tone.
So actually in conclusion I probably don't care either way what they do with it, I've got the books and the BBC versions, so they can do what they want.