I have to redo my canon... I'm waiting around to finish my evil playthrough because this way I'm finding out more and more options for everything and get to decide what I want to choose in my canon playthrough. I messed up a whole bunch of stuff the first time o.O.
Anyway, the way I plan it out, this is what I think would happen after the end.
Hawke runs off with Anders and her friends. Fenris will stick around finally convinced that slave is a slave, and that's not right, regardless of whether it's normal humans or mages who are the bosses. Aveline will fight with Donnic at Hawke's side to defend her friend and defend innocents.
Isabela will stick around for the adventure, Merrill will want to fight for freedom even if it means giving up on the mirror. I imagine Merrill will really sympathize considering the history of wars and persecution her people have gone through. Varric shrugs his shoulders "it's never boring with you, Hawke. I guess this is ONE way to get out of the merchant's guild boredom".
I imagine they all went on Isa's ship, from place to place trying to defend innocents and fight for freedom. If the Imperium attacks, I imagine Hawke and Anders would defend the land from evil maleficar slavers just as they would defend mages from templars. I imagine eventually Aveline and Donnic would connect to some small village in the middle of devastation and decide to stick around there to defend it and eventually rebuild. I imagine Isa would probably stay with her ship and sink slaver ships and other ships with templars or agents of the imperium or chantry soldiers or qun... Anyone attacking mages or the Free Marches by ship would end up in a fight with the pirate queen with a heart of gold (but she's still such a ho, LOL).
I imagine Fenris would always be at Hawke's side as long as she's trying to defend innocents and the land... he'd especially be rejoiced if the imperium decides to take advantage and attack. He'd also probably agree to fight any forces the Divine decides to send to squash rebellion. I think that if there are wars on two fronts he might be going back and forth between helping against the imperium and helping Hawke with mage freedom. So I guess he'd be on her side, but just not always there. I think Hawke would even encourage him to go to the front lines if she was too busy with templar/mage fights to go to the front herself.
Merrill would also stay with Hawke for quite some time... maybe eventually the dalish would get involved (afterall, most of the keepers are mages...) and Merrill might go and become a general leading the army. Yep, I can see Merrill eventually growing up from all the things she'd witness at Hawke's side.
Sebastian... well when Sebastian decides to attack Kirkwall, I imagine that Hawke et al would reunite to come back and defend Kirkwall. And I imagine that Hawke would get great pleasure from squashing him like a bug with her foot. Not even spells, not even! Down and dirty

.
As to Carver... he'd probably stay with his sister, but eventually go to the front lines if either the imperium or the qun attacked.
I imagine they'd all be going all over Fereldan, the Free Marches, Kirkwall, Orlais... wherever the need was. Not once caring that they might die in their quest... actually, expecting that one day they'll die defending mages or defending the land or killing slavers and abusers.
That's what I consider... a happy ending. A lot more exciting than my poor warden and her adventures with grey wardens (what does that even mean!).