Folks on this board are sometimes a little drastic. This past trip I had a reservation for 7 people that turned into a party of 14. I was unable to change the ADR before the trip to accommodate the extra guests. I asked about my chances of adding the extra people at the podium on this board, and the overwhelming response was "no way! find someplace else! never going to happen!"
It stressed me out, and I thought for sure my chances were nil. When we got there it was no problem whatsoever. We didn't even have an extra wait. While I was there, my friend who was staying there asked for a breakfast ADR. They told him to show up just as they opened, and they would have no problem.
My friend is NOT an early riser, and he did NOT get there just as they opened, but they still sat his family of 4 without a problem.
I would not approach this as a 100% guarantee, but I would say that if you get there, and ask nicely, and are patient, you have a decent to very good shot of having breakfast. Remember, this is Disney. They want your money!