Wizards will look at the outcome of GP Columbus and can decide to overhaul Legacy or not. The format has a variety of decks, and some of the more broke cards are in later sets. With an overhaul, you still get Force of Will, and everyone wants to play with FoW. I thought they were going to make the uber-extended with Mercadian Masks and up. That would include so many good sets, leaving the format susceptible to any decks. It would be like the formation of Legacy when T1 was getting too ridiculous.