If I had to guess, I would say that every QB on the board will be competing for a roster spot at camp this summer, regardless of whether they received an early offer or not.
The players without offers will be working to earn a spot in the class... unless the players with offers commit first.
Once again, this is purely speculation on my part, but the philosophy seems to be "commit now or compete for your spot this summer."
Given Meyer's comments about competitiveness in his players (he wants kids that get fired up over a game of checkers), it wouldn't surprise me at all if that was his pitch to the 2013 QBs.
Zaire and Trubisky have the inside track right now, but Chapman, Bailey, and Barrett (along with any other QBs that are offered or camp this summer) will be gunning for those two spots.
Urban Meyer is already determining each player's competitive spirit through the recruiting process- have we mentioned how good he is at this stuff?