Killian told Emma once:
So he will meet this woman,
And will fall in love again. She is always his hope
Because he would go after her in any time and universe. So I am not worried about them.
I know we have this spoilers.
But it has never stopped Killian (or Emma). He crossed worlds and time for her
And they will be together again
(I really hope we have something good. Really we don’t have all the details)