The NFLPA would never agree to drop salaries for anything. In their defense, NFL careers are ridiculously short and players deserve to receive fair value for their services the moment they enter the league because they may have suffered career ending injuries before they even hit FA. The real problem is not that the players in the draft are dictating their fair market value, the teams have been complicit in that too because they let the contracts get out of hand for top first rounders. At the same time, the players in the draft have very little real leverage because there is no other opportunity for them to go out and make even 6 figures. It's like in the Crabtree situation last year- eventually he accepted what the 49ers were offering because he needed them and that money more than they needed him.
If anything, I'd say the current CBA is unfair to guys drafted out of the first round in that they have no choice but to enter into long contracts for minimal salaries. Yet when they vastly outplay these salaries, there is no system to give them fair value until after they hit FA, which means that they may have played their most productive years for nothing and risked getting injured without getting a real payday. And sadly, for running backs like Chris Johnson, if he does hit FA teams are going to try and pay him as a guy whose best years are behind him because that is the lifespan of a running back. The only system in place for these guys is to hold out; sadly for them too many veteran players who signed market value contracts hold out two years later when they made the choice to sign a contract at that value for that duration, like Andre Johnson (who may not be holding out but is grumbling). These holdouts by multil-million dollar players trying to get a token couple million more completely undermines the situation of players like Johnson making tens of millions less than what they deserve.
I'm sure there is mutual interest in getting a deal done, but there are genuine questions that need to be examined like this one. What makes this negotiation difficult is that by nature the player's association can't yield a dime on salary, yet a more equal system needs to be devised which will leave less of a disparity in salary.