The Caspian and Dawn Treader movies both made serious changes to the plots of the books; but the Caspian movie was FAR WORSE, because it ruined the PERSONAL VIRTUES of the characters, especially Peter. The Dawn Treader movie changed the SITUATION, but the PERSONALITIES of Lucy et al were not ruined.
Let's see, what might they ruin in a Silver Chair movie? I speculated on this long ago. What I dread is that, in portraying the abuses of Experiment House, the script might change Experiment House into A CHRISTIAN SCHOOL, blaming followers of Christ for all that evil.
But I will give ANY new Narnia movie a fair chance.