It's still far too early to tell, but from MTGO, which might move faster than real tournament data and inform the metagame shift, it's already looking like a lot of combo vs. aggro-control in Legacy. Since Miracles was dominant for so long (discounting that it took a back seat to OmniTell decks during the Dig Through Time era and that it had a brief adjustment period during the rise of Eldrazi last year) and shut out so many decks over the years that might have had strong gameplay against other tier 1 decks if not for being hosed by CounterTop and/or Terminus, it is almost certain that there will be an exploratory phase in Legacy where all sorts of crazy stuff shows up. I expect to see an uptick in preexisting tier 2 and 3 decks, some wild new brews, and some throwbacks attempting to revive fallen decks. But eventually, a new equilibrium will work itself out. This is exciting.