Challenge mode is a separate modifier that in some cases made the raid easier(16 orb strategy for oryx). I can easily see this as Normal + challenges Hard(which is herioc+challenges) Legendary+plus challenges Now I hope I'm wrong but bringing the old raids to pass kings fall raid wouldn't make sense(light level wise). In their vague statements they didn't mention a raid so either they are waiting to tease one(I hope) or its kings fall again with a light increase and legendary difficulty(please no lol). I'm more of a wait and see kinda guy, my hopes aren't low or high.