there's only a small amount of unmined BTC left, approximately 1,100,000. While the number currently mined is 19,900,000, there's still time to accumulate BTC.
That's a weird way of putting it! As if you are suggesting that without a block subsidy, people won't be able to accumulate bitcoin! Which may be the reason for your follow up question.
Trading bitcoin (and people accumulating it) takes place on the market and is unrelated to mining and its reward. People buy and sell bitcoin from and to each other on the market. Any coin you buy from an exchange today is many "hops" from a coinbase reward. Which means in the future without a block reward, the market should not change at all. People will still continue trading with each other with the coins they have.
The only thing that changes is when "supply" of fresh coins entering the market/circulation decreases while "demand" goes up, the price should go higher. Which is one of the reasons why we usually have a big bull market each 4 years starting after the halving (supply cut by 50%).