We will only suck when Romo is done is if we fail to smartly build the team. We've been making decent moves as of late, and it would be smart of us to find a suitable replacement when Romo is done. With that said, restructuring can be a great thing to keep the ball rolling.
Now that the offensive core is in place and is young, I'm sure Romo actually envies the next QB in line. Much easier job with that line and , hopefully, run game.
Of course, I think they plan on him being around another 4 years still if the back continues to improve or at least hold up.
In any case, 9 out 10 times (in the salary cap era) there will be at least a year lag after the franchise QB retires.
People use the GB fluke situation as an example, but from what I can think of, that's only happened once or twice in about 20 years.
The teams that withstand the loss of their QB the best (not even one year setback) usually have a dominant defense.