While I really like Ace, and believed that he would survive once Luffy saved him, and being excited entirely last chapter with the way both of them fought together, I'm relatively certain he will die now.
Luffy saved Ace. He accomplished what he wanted to do. Now Ace saved Luffy, and is going to die the way Ace wants to, by saving his little brother. Ace isn't going to die helplessly as he would have on the execution platform. I'm thinking he will die here and now, even though hardly anyone in this manga ever does. Luffy proved to himself, others, and to us readers what he is capable of doing. And if this experience proves anything to Luffy, is that he's still weak. He will be forever reminded of this weakness of his that allowed his crew to be scattered all over the world and his brother to die in front of him. This would be great motivation for Luffy to become the strongest.
But if Ace does survive, it's not like it would be bad, but Ace dying in my opinion leads to more character development for Luffy.