Important Points To Note
Farewell, or See you later?:
It is noted that Ash has said, in the Japanese original version, "Sayonara", the farewell, goodbye to every travelling female, except for Dawn. Instead, both times (DP end and BW cameo), he has said "Ja mantane", which means "See you later". Obviously not definitely confirmed, but it at least implies that Dawn and Ash will reunite.
The Champion of Sinnoh herself has contributed several hints to Pearlshipping. Her most obvious is her comment during Ash and Dawn's Best Wishes battle, where she comments that "...That's because they know each other so well.", in response to Iris's remark on the tensity of the battle. Again, a clear sign that others can see how close Ash and Dawn are.