From Big Books Tiny Voices:
Speculation about the Narnia franchise has been all over the place for some time now- some people thought it was finished (the film rights have bounced from studio to studio) and those who had not lost faith were certain that the next film was going to be The Magician’s Nephew (because they had basically said as much). Have no fear- official word is in and they are moving ahead with the fourth film in the franchise, which will be The Silver Chair! Screenplay writer David Magee, who has an Academy Award nomination for his work on Life of Pie, will pen the script.
Hopefully this one is more like the first two and less like the third one. But who am I kidding, I'll see it regardless.