Limited bitcoin mining plays the most important rules for this high price of bitcoin. But it is a matter of fact that perhaps only ten percent of the people from whole world know about cryptocurrency. Amongst this small number of people, many of us have not enough money to manage for bitcoin. So we can't invest. Even in this situation btc price is so high. I agree with your concern, while almost all millionaires will enter in btc world, where the price of btc will go!!! As we don't have enough money to hold btc, it is sure that we must focus on another way.