It's been a while, but not yet time for GenCon, so I hope you don't mind my resurrecting this thread.
A lot of people are talking about the Necromancer. I think the Necro has both benefitted from and been hurt by PvS (will be good against Sirens, but not against Holy mages). In general, though, I think that the Necro is going to find it more difficult in many matches. Holy mages got a serious boost with PvS... so I expect probably two of four of the finalists would be one of Paladin, Priest, or Priestess... probably Paladin as one. Siren... I've played one person who had a good Siren book, so I know that it is possible for one to do very well... and I won't be surprised if there is one in the finals also, since there probably are people who have not had enough experience against her yet. Lastly, I am expecting a Warlock to be in the finals as well. It just seems to me that a fire-trained mage can do well in many matchups. So my top three expectations would be: Paladin, Siren, some kind of Warlock... with outside chances for Priest, Forcemaster, Straywood BM, and Wizard.
I especially don't want to see either of the new mages win, however. The spells available to them are pretty amazing. Since I am a fan of underdogs, I'd be thrilled if none of the above win... doesn't really matter to me which.