If Gerwig's adaptation of The Magician's Nephew should succeed well enough to make more than that one, allow me to suggest not to redo the Disney versions of the first three. Instead aim to complete the series with The Horse and His Boy, The Silver Chair, and The Last Battle. The last of these is likely to be the most challenging.

It seems that entry into Narnia requires either childlike innocence or the earthly death of a former inhabitant. Innocence seems to provide entry at various points along the Narnian timeline, and living there seems to have a particularly educational purpose. The entry point via decease is only shown at the last battle and the goal of continuing "further up and further in" -- which also implies an educational progression. A similar theme is reflected in "The Great Divorce", which might offer something of a nexus for former Narnians to with deceased non-Narnians who have left the gray town and learned the lessons that prepare them to continue onward beyond a mere one-day excursion. Indeed, I'd like to see a cinematic treatment of the "Divorce" story. Of course, I'd also like to see the space trilogy, but that would require a much more complex CGI effort.

One ought to consider that time flows differently in Narnia than in our world. But Lewis held Christian convictions about the ending of our world as well, and a new world beyond. In his book "The Great Divorce", he also depicted one version of what he thought it might be like, including a precursor of conditions for deceased persons who weren't quite ready for it.

Like it or not, that was the world in which Lewis placed his stories, beginning from the very origins of Narnia with a London cabbie and his wife, not to neglect the broken bit of street light that became the lantern post in the midst of the forest that Lucy Pevensie encountered in the Lion, the Witch and the Wardrobe. Curiously, though, his Calmorans in the Horse and His Boy seem to have significan Arab influences; and some darker skin tones and non-European culture may slip in here. There are hints that some Barbary pirates managed to become trapped in Narnia at some stage, creating a broader palette for that world.