No buyers mean no demand. If the market is in a Bull run then it signifies people are interested in the market, so the demand is increasing as long as the volume.
I am sure that we will never be in that stage where we will not get buyers to buy the coin, because we have those that are even using it to trade, so if we leave it for trading alone, there will always be demand of bitcoin in the market, so that should not even be much of worry to think of not having buyers that would buy bitcoin to make it continue to grow in value.
What we should be more concerned about now is how we can push for more adoption, I mean there is need to increase the growth rate because to me now, I think that the growth of bitcoin is still quite low compared to how it has been from the last 10 years, so we need things that will motivate or push people into the market, there is need to generate more of positive news to the market of bitcoin.