You should have a pretty good shot at the upgrade, as those routes will almost certainly be served with a 737-800 which has 16 clase ejecutiva seats. That said, there can be no guarantees so far out. The biggest risk is that there is an event that takes a lot of high-level people to South America on a given day. It is rare, but sometimes I see IAD-PTY or PTY-IAD sold out in CE even if coach is wide open. I assume that a bunch of bankers are on the move that day.

I can't speak to the dumping. I've never been able to figure it out.