That's not correct; Obama would not be the first governmnet official found to have held an office for which he in fact was not eligible, and under the de facto officer doctrine actions taken by him would not be void.
It will be necessary for Congress and a new president to actually repeal laws signed by Obama such as Obamacare.
Also, the Constitution vests exclusive authority in the Congress to impeach, convict and remove a president.
Even if the evidence is established in a court proceeding that the birth certificate was forged, the House would have to vote to impeach and the Senate would have to vote to convict him.
Furthermore, if Obama loses the election, as was the case with Clinton's crimes when he left office, we will hear the refrain "can't we just move on" from both Democrats and Republicans.
And if Obama wins the election with these birth certificate allegations hovering over him, the politicians and the mainstream media will claim that the voters have spoken and do not care about the forged birth certificate and therefore there should be no impeachment proceeding.
We need to both defeat Obama in the election and then we need to press our elected representatives to hold him accountable for his crimes in order to uphold the principle that the rule of law in America applies to all, ESPECIALLY those holding high office.