I've seen this sentiment many times now regarding the return of the Tomb Kings and Settra, but i just don't see it happening, atleast not in the literal sense. I think this new faction will be the new Death rattle with wights and skeletons en masse, but i also feel that the faction will make heavy use of skeletal constructs such as the Morghast and take inspiration from the constructs of the tomb kings. Also a thing to note is that the music in the video is Mongolian folk music. Also the return of Settra, i just don't see it happening, but i still see the cruel punishment that Nagash could have given to the one who never serves by making him thrall to Nagash's service. The narrator is the entity that was released from the stormvault, and he doens't look very Settra like or even undead. "He was born long before Sigmar's rise to power" that would still place him in the AoS timeline since Sigmar showed up in the mortal realms during the age of myth and just lollygagged around for centuries before he became the storm god. Also i would like some new characters in AoS, some characters that can give the setting an identity of it's own and not just rely on the already established charaters of the world that was. My guess is that the new death army will be skeletons, but it will feature a lot of eastern/egyptian designs and it will be a sort of spiritual succesor to the Tomb Kings.