I've heard that Bitcoin will finish mining in 2140, which is certainly a long way off. There's still a chance for us to continue dca BTC, as there's a strong possibility that in the future we'll see a higher BTC price than today, as BTC is constantly being mined, and we'll eventually see the BTC supply dwindle. Currently, I know 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.
However, I'd like to know if there will be BTC miners once the supply is fully mined, and will the fees for sending from wallets to exchanges be high? I also wonder if the price fluctuations will be similar to the current bearish and bullish market. Currently, BTC is widely traded, buying at a low price and selling at a high price. But will BTC trading be possible in the future, similar to daily trading? I think this is worth discussing...

If we talk about Bitcoin's future, it is all speculation based on individual opinions or analysis. For me, Bitcoin trading in the future is still possible, because as long as Bitcoin is still running and miners are still around, so we can still imagine that traders still possible do trading Bitcoin in the future. Another reason, miners will continue to exist is because even if Bitcoin is completely mined, it is still possible for miners to profit from validating network transactions, cmiiw. Therefore, we can take advantage of the current momentum to accumulate Bitcoin, as you mentioned, because I believe we are still in the early stages.
For reference, we can read it here:
What Happens to Bitcoin After All 21 Million Are Mined?