Sabin and Edgar share an ending, but Sabin is the star.
For an ending to leave me completely satisfied, it has to have a couple of things. I want closure -- answers to questions I was left asking during the game, and I want to know what's in store for the characters next. Edgar and Sabin didn't die, so what's next for them now that they've defeated Kefka? While the latter is left to imagination, Sabin and Edgar's ending gave me enough to certainly answer any questions I had, and enough to make a probable prediction as to what's in store for them next.
The ending starts with Sabin, Edgar, Setzer, and Celes running. They come to a locked door, and Edgar tries to pick the lock. All of a sudden the room shakes, and a pillar falls from the ceiling right where Edgar is standing. Sabin gasps, runs to his brother, and catches the pillar before it can fall on Edgar, saving his brother's life. He pours out his heart to Edgar, and then throws the pillar with his super-human strength. Edgar successfully picks the lock while Sabin is holding the pillar, and after Sabin throws it, the four run through the open door.
I think Sabin poured his heart out to Edgar because Edgar could have died there. It makes sense if you look at what he said. It almost sounds like a confession.
I didn't turn my back on the kingdom, big brother. I knew you'd be a better king. I trained hard knowing I might have to help you one day. Now I know why I have these stupid muscles!
He wanted Edgar to know that he does care about him, and about their kingdom. I think this is especially important because the kingdom was mentioned in their father's last wishes. Doing what would have made his father happy and proud was important to Edgar, and by becoming king and giving Sabin freedom, it seemed as if Edgar had sacrificed everything.
Sabin definitely cared though. Sabin's motivations and intentions were unclear throughout most of the game, and while I was able to make guesses in the right direction through his actions and dialogue, it's great that it is spelled out in their ending.
As for a future for Sabin? The ending reveals that everything Sabin had done had been for his brother and for Figaro. I don't see why that would change after the game. I think the two return to Figaro and strive to help their kingdom recover from the attacks of Kefka and the Empire. I also see Sabin and Edgar becoming very close. They were reunited after ten years in the worst of circumstances, so they still have a lot of reconnecting to do. I think they will work on getting to know each other again.