Is it true that the older oranges are, the more they become alcohol?!
Just like grapes they will have a certain amount of natural yeast on their skins, eventually as they decompose the yeast will cause the sugar in the orange to ferment, however when the alcohol content reaches around 5 - 8 %abv, the alcohol itself will kill the yeast so it won't get any stronger than a weak wine.
They might get slightly alcoholic - but not enough to be worth drinking. More likely they will just go mouldy