I now they all have biological warfare weapons. But remember that even the best of these weapons there will always be people that will be able to survive. Also even the elite will not really need to go under for years since they have vaccines for all these biological viruses.
The elites will go under until it is save for them to come up from all the civil unrest.
But like 74 the total global genocide will not be something easy to do. I think they may plan to do smaller global genocide events.