The law of supply and demand is as fundamental as the laws of physics.
If supply is fixed, and demand increases, price will increase, always.
But it's a mistake to even think about Bitcoin in terms of USD price.
If everyone starts transacting in Bitcoin, the legacy currencies become worthless, so in time the exchange rate becomes irrelevant.
What matters is what Bitcoin can buy.
If everyone is using Bitcoin, and the global population keeps growing, then the distribution of Bitcoin among the population gets thinner and thinner.
With each passing year it costs less and less Bitcoin to buy the same goods.
This is the opposite of the financial system that we have grown up in, where inflation is the norm and it costs more and more dollars to buy the same goods.
