I just wonder about the closing door though. Doors are hugely symbolic in art. (Warning: Ariel in movie-analyst/critic mode below. )
I like the callback to the door-closing in LWW (and VDT and PC), but on the other hand... is it really the ending of a story? Is there a need for a literal closure? I mean, it's definitely the end of the story for those of us still on this side of the stable door, but on the other hand, Lewis did describe all that we know of Narnia as the title page and only now does the first chapter of their adventures begin.
And on a more spiritual/intellectual level, closing the gate could give an impression that Aslan's Country (/Heaven) is closed off. Of course, not everyone in the audience is going to think of it that way (Narnia's not an allegory, after all!), but because doors so heavily drip with meaning, questions - even subconscious ones - could well be raised. Closing the gate will bring up certain questions while leaving it open will bring up others.
Even if we drop the spiritual part (namely, the Heaven question), the gate can still have meaning for the audience. Just look at the three movies we have so far.
- LWW. Having Digory, rather than Lucy, close the wardrobe door is telling: she wants more, he knows that this particular story/adventure is over. And then having the door crack open again and letting light and Aslan's roar through says that there's more to come... later.
- PC. The train doors close on the Pevensies, giving a sense of finality. It is, however, lessened in its impact by a couple things. The first is "The Call" by Regina Spektor, holding a hope and promise of return. Another is the train leaving: on the one hand, Peter and Susan are moving on, but on the other, there's more in store for Edmund and Lucy beyond the black of the tunnel. The third is Aslan's roar. "I'll come back when you call me", anyone?
- VDT. Unlike LWW, Lucy herself closes this door. It's the end of her story, the story she began by opening a door. Sure, she takes one last look at Narnia (as the ship disappears behind a wave), but like Edmund (and Peter and Susan before them), she's moving on. Now, I'd always wished that they'd inserted Aslan's roar, just as they had with the first two. I probably still do. But on the other hand, from Lucy's perspective, she shouldn't hear his roar. There's no return till she returns to stay. (So great, now I'm on the fence about the lack of an ending roar. Great job, Ariel.)
(*falls back to catch her breath* Oy, that turned out way longer than I thought.)
All that to say, "I love your idea, Esprit, but I think the gates should remain wide open." And if we want a finalizing touch, cue the credits with "This is Home" by Switchfoot. (Why in blazes is that song for PC anyway? They should have saved it, no matter how many years it took, for LB.)