It isn't that Rodgers is past his prime... he's still got some awesome years ahead of him.
The problem is what it would take, and the time it would take, to put a championship caliber team around him. So many of TT's draft picks are pedestrian or worse... Rodgers would really have to play at a super- human level for us to win another championship.
Add to the talent deficiency the fact that Capers is still our DC (the game has clearly passed him by - what is he, 80 years old now??), and we simply don't have a realistic shot at another SB in the foreseeable future - which is probably the rest of Rodgers' career.
If they fired Capers I'd be more optimistic, but it is pretty obvious that Capers isn't going anywhere.