The death's never truly happen

After much speculation, i've given a lot of thought to the deaths of our leaders. Blizzard stated that they will either die, or lose hope. This is the greatest invasion ever to come, and we will be tested to the limit. This is why I believe that instead of dying, our leaders turn against us and join the legion. Their faith is tested, their hope fails, and they become the very enemy we are going to fight. It has also been stated that Anduin will know the meaning of true sacrifice. Could this mean that either himself, or his father, give in to the legion to seek out the power to save Azeroth for good? This could even open the possibility (doubtful) of the legion being a faction option for other players?