Inheritance question

InheritanceChristopher PaoliniWe know that there is a high possibility of a book 5, as it has been hinted and openly discussed many times, but I feel like we never consider the possibility of the story taking place from the P.O.V. of a different person significantly later than where Inheritance left off . Here is my hypothesised plotline start for this idea in order of events:
Inheritance ends and Eragon goes to the island.
Time passes and Arya gets disillusioned with the Elves or the Elves leave Alagaesia.
Arya travels to Eragon
Arya and Eragon have some form of romantic relationship
They get married/some equivalent
Time passes
Cue book 5
Problems beset Alagaesia
Random person, most likely a child of one of Eragon's friends from the book, i.e. Rohan, Joad, etc. arrives at Island
Eragon and Arya train child
Problem besets Alagaesia and Eragon and or Arya try to stop it
Eragon and or Arya die
End of book 5
What do you guys think?