This showed up on wow.com earlier this morning. Haven't seen it posted so I figured I'd throw it out for you guys. Be warned as it contains SUPER spoilers!
It seems like we get turned into Scourge, which is probably where the blue/green/red/black beams come in from and then Tirion does something to return us to the living. Then, I guess we get pulled into Frostmourne at one part, fight our way out which damages it and bring the Lich King down to a certain point where he starts casting remorseless winter and we need to kill him before he kills the raid.