Ah, season 3 OST is out - finally.
Warning (book) spoilers:
Hmm, the final track is called "For the realm". I wonder what the final scene of the season will be.
Listening to it, it's just an acoustic guitar solo of the main theme. Probably Mysha is the finale then, so Danearys will be the last scene. I was kinda hoping it would end with Coldhands or un-Cat. Those would be some epic cliffhangers.