The rankings don't tell the whole story right now. Consider that Sloan, one of NU's verbals is a very soft committ and likely won't end up in Lincoln. Look at Kansas, right above NU on the team rankings. 3 of their verbals aren't even ranked yet. Dave Clark, the juco CB will end up being a 4 star and Mundine, the currently unranked LB will be an easy 3 star. Who knows if their kicker will ever be ranked. Rivals only ranked 10 kickers last year and all 10 were 3 stars.
Bottom line right now - lots of quality kids are not ranked yet, there is going to be a lot of movement in the next 6 months. On a side note, what a class Stanford has coming in so far. I like to see that.