If Trump wins, then it might open up the possibility of investigating whether or not Obama really is Constitutionally qualified to be president, if he isn't then that would invalidate the pardons.
THAT IS...if he even has a congress or senate willing to back him.
Without them, anything he tries is moot.
Remember, to go after Zero on ineligibility, he has to go after everybody else involved.
In order to get things done, he HAS TO have people on his side.
It just might be better to let sleeping dogs lie.