I really can't imagine Dawn staying. If she does, then we would have to deal with that annoying penguin of her's for another few years, and the electric rodent will always be the main mascot, the penguin only represents DP.
And if you compare how long each of the three main female characters stayed in the show, it would only seem natural that Dawn's time is up. Misty was around for about 5 years, May for 4 years, and Dawn is at 4 years now. Of course, the writers can easily decide to break the pattern, but I don't think they would do that.
Also, what is happening this week in DP180 sorta reminds me of the episode where May met up with Drew again and got snapped out of her somewhat depressed state. Like Dawn's current situation, May didn't have her future decided at that point, and the episode served as a way to set up her eventual departure. In the same way, DP180 should most likely start setting up Dawn's departure, which will include a later episode involving Zoey and/or Ursala.
Assuming Dawn leaves, it will be after the League. As some have pointed out, there is already proof that she appears in DP181. Plus, can you imagine only Ash and Brock traveling together? That just doesn't make much sense, Brock would actually have a big role o_o.