The highest first-round pick that has signed to this point in the off-season is linebacker Luke Kuechly, who the Carolina Panthers took with the ninth overall pick in April's draft. The top eight picks are still unsigned, and Tom Pelissero of ESPN 1500 has a good reason as to why that is.
Per Pasquarelli, all eight teams are pushing for so-called "offset language" that would take them off the hook for a player's salary if he is released before the rookie deal is up and subsequently signs with a new team.
As Pelissero points out, if you're dumping a guy before the end of his rookie deal, he's probably going to have a hell of a time catching on anywhere else, and the team in question probably won't have to worry about paying him anything anyway.
Matt Kalil is likely in line for a contract in the neighborhood of four years, $20 million, with an option for a fifth season. I don't think we're going to have to worry about the cornerstone of the offensive line for the next decade being a training camp holdout or anything like that.