I'm here to say it is not!
The susunod movie will be The Magicians Nephew.
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soro (instead of Disney) decided that they will be skipping the Silver Chair and just going on to the Magicians Nephew.
I am very sad that the Pevensie will not be there.
I think another reason they are doing TMN is because many people say it is their paborito book after LWW.
soro is hoping that TMN will have a better turn out than the Voyage of the Dawn Treader.