If tomorrow the 5 permanent members of the United Nations Security Council (China, France, Russia, UK, USA) and their atomic weapons decide to cancel the Antarctica treaty, then the treaty is void. They can invite to the ceremony the other members of the UNSC, but I guess it's better to invite the other countries with atomic weapons.

They didn't cancel it yet because for now there is currently no activity there with a profit, and they are not sure how to divide it. But once there is a way to gain money, don't expect that the treaty will last too much.