What about the people who got letters about shutting off their
public peering? What will they revert to?

Would everyone who has received such a letter from some peer and who is
running defaultless please send me some mail? I'm willing to go under
NDA if that's the only way you can legally part with the information.
I'd like to be able to report back to NANOG the number of such events
which are now pending, even if I'm disallowed by NDA from naming names.

Right now it's just a rumour. I'm willing to help upgrade it to a fact.