The world may never know. Maybe since the other girl trainers visited in the last regions, that would have to make Dawn come, pretty much. Maybe it turns out that Dawn likes Ash or something. Who knows. I haven't watched the last two episodes since I have been at my aunt's for about two weeks. (They don't have internet.)Overall, maybe Dawn will want to catch some new Pokemon, like Meloetta. I do know that she will encounter it the Pokemon. But I don't know if she catches the Pokemon. I'm in the U.S. so I don't know if the show is out.
What I know:
1. She comes to the Unova.
2. She encounters a legendary Pokemon.
What I don't know:
1. What team she might have.
2. If she catches the legendary.
3. If she likes Ash. =P
I hope this helps! :)