I think that the price of the Bitcoin will stand still or even become less worth. Because no one uses it, it can't grow in worth.
But I personally don't think that this day will come because there are many people that use Bitcoin and this can only happen if the internet gets shut down for days all over the world.
i think the op want to know that if all the people stop using bitcoin mean that no one is ready to sell their bitcoin, then what will happen. so i will like to add that if all the people of the world will stop using bitcoin and will hold it, then the demand of bitcoin will continuously increase which will also cause the price to increase.