It all comes down to your QB. The question should be; is your team's QB good enough to win a Super Bowl. If not, it doesn't matter how often you've been to the playoffs, you should be looking to upgrade. What do Stafford, Smith, & Tannenhill all have in common? They will never (did I say never? I meant never) play consistently good enough to win a Super Bowl, let alone even make it to one.
To me, TT is an unknown. Sure, he won't beat anyone with his arm, but he sure can beat you with his feet. 6 points is 6 points.