The central banks will be forced to temporarily buy it (as they have been doing since August) otherwise we could have a self-reinforcing 'bank run'. As in the early 30s, the bank must put its cash in the 'front window' to assure everybody who may want their money, that it is there.
That's what the Fed is for - the buyer of last resort, to restore confidence when everybody else is in full panic mode.
BUMP
The firm I work for, only lets us sell A/A rated bonds. If they fall below that, we can’t buy them for clients. Problem is, a new issue A/A, is just tomorrow’s BBB, BB, B....
So, I can originate the sale at the worst price, but not take advantage of it later, at the lower price. Duh...