And that is the more reason why we don't need to expand or increase the total supply.

The lower the supply, the higher the demand and that also means the higher the price of it. Another thing is that not a lot of people will be using Bitcoin since most of them will stick to the traditional payment method. Don't also forget that there are a lot of Bitcoins lost in the total supply, that means the total supply is not really 21 million by now.