Tyranids eat man , elder , orks and Tau ( and anything else that's eatable )
Chaos dies ( nothing to sustain them )
Necrons sit and wait till the tyranids either starve ( or turn on themselves to sustain higher hive creatures ) or bugger off .
Necrons are now the rulers till the destroyers get bored and decide to anhialate the last living remanants ( ie , the other Necrons ) .
simplistic I know , If you follow the fluff though the silent king came back from his self imposed exile once he realised the threat of the Tyranids .
The problem with simplistic solutions is that all the greatest threats in the galaxy are occurring simultaneously. So for example, whilst the Tyranids are encroaching from the galactic void, Chaos is also breaking through the Cadian Gate and enacting the Crimson Path, whilst the Silent King is strenuously reawakening Tomb Worlds etc.
In the relative short-term the most likely outcome is the 13th Black Crusade (thanks to the Crimson Path) rumbles on towards Terra, just as the Astronomican continues to attract the Tyranids swarms. The primary purpose of the Silent King and his awakening Necrons seems to be to combat the Tyranids, whilst any and all Greenskin empires will continue to be attracted to the most vicious wars. Thus a four-way scrap (with involvement from any Imperial remnants and any interested Eldar factions) over the carcass of the Imperium seems the most likely result in the short-medium term, which would then usher in the next age of the galaxy.
Heresy's Background FAQ. (Fluff Project)
I do love how we don't even need CotE to comment anymore, chances are he has already said something intelligent before that can be re-applied to the current situation.
CotE Reviews: Prospero Burns (HH Review)
, Age of Darkness (HH Review)
Last edited by Child-of-the-Emperor; 08-13-13 at 03:51 PM.