Guys guys...there's nothing confirmed yet. It was most likely a mistranslation on DiamondClass's part, but for now let's not get too excited and in over our heads. The lower your expectations are the better you'll feel when you find out the full details.
As trustest_friend said, it will probably be a mini ~5 episode arc. We can still hope (like I said, nothing is confirmed), but this is what we will probably receive at least.
Anyway, let's move away from this topic of whether Dawn will be there longer or not. The point is SHE IS GOING TO BE THERE, period. We should focus on what ifs and speculations on how she and Ash will interact upon seeing each other.
Sooo...a new topic!
What kinds of interactions would you like to see between the two during Dawn's stay?
(And try to stay as realistically to the show's style as possible. Although letting the imagination run wild wouldn't be so bad either. ;P)