Speculation has arisen that the Kris Jenkins trade rumors are to spark a defensive revitalization - to get younger, cheaper. I disagree with the premise - this draft will bring needed depth and talent as it is.
Jenkins is only 27. He's signed, reasonably, through 2009. He fails the criteria of being a cumbersome contract or aging out. Replacing him would be two veterans - Maake Kemoeatu is highly paid, and Damione Lewis is a free agent after the year. The top backup in that situation, Jordan Carstens, is a free agent after the year as well. There's no push (or even room) to get younger at DT. The team needed to get younger at DE anyway - and Mike Rucker will be phased out in a year or two anyway. Jenkins gone wouldn't change that. Julius Peppers needs a huge extension regardless of Jenkins, Rucker, or anything else on the team.
The defection of Will Witherspoon last year may have spooked the team a bit; the team's lost out on mid-20s re-signings like Marlon McCree. So far, the team has passed on getting 20-something talents like Kawika Mitchell at cheap prices, and other young players like Ken Hamlin and Kevin Kaesviharn signed short term deals.
The secondary, save Minter, is young - at least one starter will be a rookie this year. Ken Lucas is next oldest at 28 - he and youngsters Gamble and Marshall are all under contract for at least two more years (Gamble, not likely to start, is the only one signed a year short of 2009). While extensions may become necessary, none of these players are going to require any heavy, long-term extensions like Peppers.
As well, linebacker isn't an old position for the team; Thomas Davis enters his third year, as does backup Adam Seward; James Anderson enters his second. Na'il Diggs, at 27, is the "old" guy in the group. Dan Morgan isn't old but will be replaced in the short term anyway. The team actually needs a bit of veteran leadership here long term.
Which leaves end and safety, as noted - two positions the team already needed. Add in a long term solution for Morgan, and the team's already much younger. Dropping Jenkins for great value is one thing; youth makes no sense. Youth will come regardless.