It will not come to that point. There will never be a Bitcoin shortage. The value of Bitcoin could adjust up to whatever point it needs just to satisfy the demand and the necessary valuation when the entire world will be using Bitcoin. If the demand is rising so high due to the billions of people across the world using Bitcoin, the market will be assigning a bigger value to every Satoshi. There are eight decimal points in every BTC. It may happen that .00000005 BTC will be valued 1 USD.
Yeah it will not come to a shortage instead the market price will be ajdusted meaning to say bitcoins will go high on its market value if people around the world will invest on bitcoin. This could be very interesting to know that if this happen one that hold 1 BTC will relatively get 1000x fold of money invested.