This is considered a theory. This is also non-canon. Ok the ending would be this. This is years into the future. Ash is either married to Misty or Dawn (way mais likely Misty) and haves a daughter. Ash is not in the video (link below).
Well the Dawn thing would make no sense so I will explain.
In the beginning of the video, on your right is future Misty. On your left is future Dawn (possibly). And the middle is Ash's daughter. Well if you are still confused about the Dawn thing you can see that on your right in the video it's a woman in blue hair. It's obviously Dawn (likely).
Here is the link: link