Tyrion will seat on the Iron Throne.
Don't ask why I'm saying that, I know it's technically impossible... there would need to be too many twists for that to happen and even then...
I just like the idea.
But I do think he'll have a major role in the end and that he could be the true hero of this story.
Maybe he'll kill The Mountain (how cool would that be huh ?) and his brother will kill Cersei.