I spoke with the USAF chief of fighter manning last week, he doesn't know the exact answer to that question which probably means nobody knows. He can tell who has gotten out/dropped papers, but there is really no way to predict what people who haven't shown their hand will do. No direct quotes, but I got the feeling he is well beyond extremely concerned. I joked that this year he's paying pilots to leave and next year he'll be paying to bring us back, and if my poker face reading skills are up to par, I probably wasn't too far off the mark. I personally know 4 sitting/graduated squadron commanders who either have, or will drop papers when the time is right. That said, not everybody who leaves the military will go to the majors.
On a related side note, a friend of mine with buds at AFPC just dropped papers to avoid a 365. His AFPC contact told him that for every 365 they try to assign, on average there are 25 officers who wriggle their way out before they actually assign it. That includes a large number of individuals who choose to separate/retire instead of spend a year making sure the general gets his 12 point helvetica on the 1st sub-bullet of each slide.