As the players return to Cedar Valley with the Orb of Storms, ask if there's anything else they'd like to do before we end the story. Don't volunteer anything, just give them the chance to tie up loose ends.
They probably want to think about how they're handling the werewolves. Do they have a way to control them? Would they like to bring them back to Cedar Valley and get them cured of lycanthropy? If no, does it occur to them that they should cut down the bridge so the werewolves don't get into the Empire?
Do they remember to go back and get the Ambassador?
I've had players tell me that, as they leave Freehaven with the Orb, they chuck their flasks of alchemist's fire into the city, setting the place on fire. Kind of a dick move considering the druids were the only real villains in the city, but "walking away from an explosion" is a good way to end a story.
If the players don't think of anything they want to do, that's okay too -- don't prompt them.
If you've actually run this adventure, you should mail me at danb.boardgames@gmail.com and tell me how it went!