The Pevensies and Eustace ended up staying in Narnia, no reason to go home. The Pevensie's parents had died, and Eustace's parents disowned him for liking Ed and Lucy.
The two families decided on ruling Narnia together. Peter, Eustace, Caspian and Edmund the kings, Susan, Elizabeth and Lucy the queens, which ended up being really helpful. One of the Kings and one of the Queens could be in charge for a bit while the others were helping with the five kids. And no, I didn't mean to type four kids.
Caspian and Susan got married, and are currently expecting a baby boy.
Marku and Elizabeth are done having kids. Four was enough for them.
Caspian and Elizabeth grew even closer than they were before, yet Elizabeth grew more independent without him.
That was the reason for her test, to learn to move on for when Caspian actually dies. She had learned to be fine without him. Not happy, not great, but fine.
Caspian and Peter would occasionally fight, but overall put their differences aside for the good of Narnia.
The End.