I took a shot in predicting the Seahawks' final 53-man roster, looking at roster locks, roster battles, and roster longshots. In doing this, I broke up the roster into offense and defense, and grouped them by draft year (as a proxy for age).
This first table below shows you how young the roster is (it's heavily weighted at the bottom, 'the foundation'), and it's also worth noting that only 12 players on the roster were drafted before Pete and John came together to form "PCJS".
I also predicted (in yellow) the 50 man "offense/defense" roster, obviously excluding specialists. This is almost assuredly going to be very wrong. I also took a stab at the practice squad (a fool's errand). Injuries and competition will shake and move things around - which is the fun part of the offseason, and obviously, Seattle likes to shuffle their practice squad weekly.
No one knows -- not Pete Carroll, not anyone -- who will rise up and stand out, and who will get left behind when the season kicks off. (This is why we all love this sport's offseason).
Lastly, 60 of 87 Seahawks on offense/defense began their career as a Seahawks (either via Draft or the Seahawks were their original NFL team as an undrafted rookie). This is a huge number.