I think a way they could end Ash's story is by him going with Dawn to help her complete her dreams. while yes, she has completed things offscreen she has not completed her goal. We could see Ash decided to go with her to help her complete her goal at the end of the special 11 eps. Also implementing that they have a romantic future together, after everything that they have to do together in JN it's more than obvious that the writers ship them together, I know Tomioka will be writing the ep and they left Dawn's story incomplete in JN the only pokegirl yet to complete her goal.
Ash x Dawn
probably similar to pick related
this would both preserve 2 popular characters(both MCs) for future use
both have shillmons(Pikachu and Piplup)
keeps them in a state where returns are possible.
>>52792616A child for each of the special legendaries
lake trio
4 Sinnoh legendaries
2 johto legendaries
and 2 more for another Piplup and Pikachu(not Ash and Dawns but maybe their descendants)
