I agree.
More worries are currently about how much the retailers, common people would possess BTC and their proportions to bigger entities in the long run in the eco.
However, that's too a question that would be developing over the years, if not decades to come..
There is no worry here. Bitcoin is divisible, 100M satoshi is 1 Bitcoin. You can buy a fraction and you are good to go. If it does become a problem, solutions will develop quite easily. You can issue other things and have them backed by Bitcoin at a fixed rate. Very easy.