I think the bitter part is going to be that he finds the time portal destroyed and realized that he can never go back to the past to save his family.
Aku said he destroyed all the time portals. In this next episode Jack travels to the Guardian's time portal.
Not to mention we have too much left. What about the Scotsman's daughter's new army?
My theory is that the time portal is destroyed, Jack is either found by or finds the Scotsman's new army, and he will lead this army to one final battle against Aku where he will finally defeat him, restoring peace to the world and becoming the DeFacto ruler (hence why we see his future version through the portal wearing a European style crown and garb)
just my theory though. It makes sense to drive the plot in that direction.
I honestly don't think they will kill off Ashi and leave Jack completely alone again. He just found his hope again, and it's all because of Ashi, her transformation from Aku-loyalist assassin to an ally and love interest. She resparked his hope in his darkest hour. To kill her off would make for one hell of a dark ending.
Is it possible? Definitely. Will it happen? Maybe. Whichever ending it is I just hope it's a good one. We've been waiting a long time.