Our democracy relies on the results of a nationwide vote, administered at a specific moment in time. Even if the demographic changes hours later, it is not practical or reasonable to expect that we should override the outcome of the vote because of a demographic shift.
The outcome of the vote was final. It must be respected. Otherwise, how often do we have to have nationwide elections? Every year, to account for shifting demographics? Every six months? Whenever there is a significant demographic change? This is not practical.