That's not apocalypse, though. That's just the normal economic cycle.
If a company actually thought the apocalypse was coming, why would they buy back stock? The stock's going to be worthless, and so is the company. Use the cash to buy something that will be worth something in the apocalypse (food, bomb shelters, guns, maybe gold). If you actually believe the apocalypse is coming, buying corporate stock is a stupid response.
So I don't believe your claim that stock buybacks indicate that corporations know the apocalypse is coming. Rough economic times, sure. Apocalypse, no.