This is misleading because, while this frees up "a lot of cap space", you have to consider that they are already at 141, so if this does free up $28mm, that brings them down to 113. So, they have roughly 7-10mm in cap space going into 2013.
But, you didn't account for the losses they'll need to account for, starting with those three players, then the free agent losses, who are already accounted for in the cap savings:
Likely Cuts- 3
Jason Smith
Calvin Pace
Bart Scott
Unrestricted- 12
Yeremiah Bell
Mike DeVito
Nick Folk
Shonn Greene
Dustin Keller
Laron Landry
Aaron Maybin
Brandon Moore
Chaz Schilens
Matt Slauson
Bryan Thomas
Jay Richardson
Restricted- 4
Jeff Cumberland
Austin Howard
Joshua Mauga
Tanner Purdum
So, there's 19 players to replace on, being very optimistic, $10M in cap space. I'm sure they'll try to do some maneuvering and push back contracts into later years, but this is no longer a place where a veteran is willing to do a deal like that. Moreover, it's unlikely current players would be willing to mess around with a clown franchise and restructure. If they cut Sanchez, they'd have about half of that cap space. The QBs you mentioned? That's a pipe dream.
Do the math, it's roughly 500k per player at those positions.