Most events have at least one minor to major upset. For the upcoming UFC 67 I think the 2 bouts that could garner upsets are Griffin vs Edgar and Silva vs Lutter. We know the undercards because they are way under. I will be pulling for them come UFC 67.
Silva-Lutter could be an upset, but probably not. New Rampage has not been as impressive as Old Rampage. But, Eastman probably doesn't have the tools to win this rematch. I'm going out on a limb and saying Machida-Hoger.