Yes, probably isn't, but Warhammer Fantasy Battle and Warhammer 40k are essentially in the same universe, just in different time periods, and Warcraft (and Starcraft) were heavily inspired by Warhammer. It would make since that the Draenei were the first descendants of the protoss, and that the humans of Azeroth used something like the Dark Portal to colonize Earth, and that Sageras was not defeated by ancient heroes but was frozen in time. Scourge could also have been the first 'Zerg'. Since the Titan's created both the Draenei and the Scourge, it could make sense that they are the Xel'Naga. Then again, assuming something like that is saying that Diablo and Sageras are the same, just that Sanctuary is some world in the Twisting Nether.
P.S.: Ok well, what about Project Titan? You know, Blizzard ultra secert and supposedly awesome world changing MMO. Perhaps there is a connection?