Once you finish the narrative in TTK (story,raid etc) you will unlock a mission that explains what happened to Praedyth in the VoG (it's in the vault as well) and where he is now! I'm so excited for TTK! If your negative please don't comment thanks.
This was confirmed by Game Informer Magazine
-
Look at the description on praedyths revenge. Apply it to the current state of praedyth and it proves hes alive in a different timeline