The Pevensies would not return to Narnia. Peter and Susan had already accepted this and had moved on with their lives. Edmund had tried too. Everyone except Lucy. She couldn't imagine a life without Narnia. However, as the years passed, Lucy lost faith and cared no longer for Narnia as her siblings. When the Great Lion becomes aware of that, he sends a 17 year old Lucy Pevensie back to Narnia.