Meh. The exile was never betrayed in his heart, methinks. The council cast all those out, who followed Revan's crusade, so the exile's, well, exile is really just an affirmation of their early choice to exile them all. The exile is special there only because he was the only one to ever return and face judgment.
The exile was never close enough to Atris to really be betrayed in his heart by her. Atris loved the male Exile, but he didn't know it, and so never returned those feelings. And besides, even if he had, the male exile is just an option (and not even the canonical one, which is sad, if you ask me...)
The exile is never given any particular reason to trust the masters in TSL, and given how Kreia treats the exile, I doubt there is any love lost there either. So no, I wouldn't call any of that "betrayal in the heart" either.
The best candidate now is Revan or someone we haven't met yet IMHO. I don't think the writers of K3 should feel compelled to write a third Darth Traya into the plot, though - I see no overwhelming need to. Even if Kreia is right, and there must always be a Darth Traya, that doesn't mean that this person must ALWAYS be significant in the plot. Where was Darth Traya in K1, for example?