This speaks of a time when the big mega banks all across the world will collapse and implode due to a major catastrophic economic event. The most likely thing to cause this is the coming global economic collapse in which very few banks will survive.  Or perhaps this may be a separate event that precedes or precipitates the global economic collapse.  Nobody is quite certain.  All that is known is that at least one mega bank (the two big to fails) will ultimately fail causing economic hardship on a LOT of people and companies the world over.