In regards to the op, I can see this being valid, the 8th seed gets a more level distribution of robot ability available to them, and having solid picks for all the members of an alliance makes a difference. Depending on the depth of the division, and the luck of the eighth seed it certainly is possible. An example of this that I enjoy is 2012 Galileo quarters.
8 takes 1 in three matches.
http://www.thebluealliance.com/match/2012gal_qf1m1
http://www.thebluealliance.com/match/2012gal_qf1m2
http://www.thebluealliance.com/match/2012gal_qf1m3
Teams that scout effectively at champs are going to have a huge upper hand. There are going to be a lot of robots that go under the radar, and in this year more than others I believe there will be upsets at champs.