I do not think that bitcoin will be enough if the whole people around the world will going to buy bitcoins. There will be too much shortage on bitcoin supply and this will lead also to have an expensive market price for bitcoin. As we all know that there are billions of people around the world and bitcoin supply is only limited. So meaning to say in the near future there will be a shortage for bitcoin supply and thus will lead to create another dominant coin like having ether as one of the possibilities that it will be the next to bitcoin. As of this moment i am seeing this already closely to happen. What do you think?
If the demand of bitcoin increases and if the billiion of people are using bitcoin, i think you anticipated well what will happen in bitcoin in the near future. The price of bitcoin will rise up and people can have a satoshi valued a $10k each i think it will be enough for the demand of billion people. But there are alternate of bitcoin, that is why there are lot of altcoins created to alternate bitcoin to replace some part of it to use as payment, etc. Increasing demand wont be a big problem in crypto currency.