I'll be helping out with running the tourney, so I won't be playing... But a quick look at the card lists (VERY preliminary), I'm guessing Blue will be very, very good. On the other hand, undefined environments have a tendancy to lean towards beatdown, so it could swing either way...
But really, look at the cards! Blue has _everything_. Control Magic for a bit of card advanatage, with Mana Drain, Force of Will, Force Spike, and good ol' Counterspell as backup. Browse provides card advantage, and thins your deck. Hell, Thawing Glaciers is legal, how can blue NOT dominate?
I'm guessing Draw-Go will be very, very popular.
Which brings me to my next point, beating the metagame. With Draw-Go all over the place, I think Burn might do well too... Since players have such short notice to build decks, expect a lot of speed as well. Alliances offers some great additions to a controllish old-style Sligh deck, Balduvian Hordes, Death Spark, Guerrilla Tactics, etc... Might have trouble with early countermagic, which is, as I said, a big deal.
But there's Burnout, Pyroblast (which has it's opposite too), etc...
Hmm... Now that I think about it, I see White deeply troubling both of those decks, Keldoran Outpost, more importantly... That'll beat up Blue badly, and there's some nice blockers to stop Red. I dunno...
Gizmo, any thoughts to add, or would you just like to cut mine to shreads again? You're the metagame theorist, not me!
Go to it!