Such speculation ignores the Clintons' mastery of triangulation.
It is far more likely that she would replace Biden on the 2012 ticket. She would signal that she would be able to perform her baby-sitting duty much more effectively, Bill would campaign for the ticket on the premise that the nation would be getting a 3-for-1 deal etc. Remember, if Mr. President wants to stay in the White House, he cannot afford to lose his radical base but he must also maintain those brains full of mush who call themselves
With the moderates entranced by Hillary, and the Democrat Cheerleader Media (DCM) constantly reminding them of how the Republicans will burn churches, bomb abortion clinics, establish LGBT concentration camps —you know the drill— Obama/Clinton might even have a decent chance.
And, if they win, Hillary gets to be the nominee in 2016.
Two primary wins without even having to run.
My guess is that the Clintons do not necessarily have the hunger to try to mount a primary challenge at the end of which they know they will not win the presidency back. In that case, Hillary for VP would look like an eminently doable alternative.
Unless, Hillary wants to signal that she is abandoning a sinking ship, say, some time around June 2012, and ensure that Mr. President goes down. It all boils down to which one is the stronger motivator for her: Ambition or revenge?