So BTC will continue to be mined until about 2140, when all 21 million are finished. But imagine if there were 21 trillion bitcoins and it finished in say the year 9140, it actually wouldn't make any difference to us than 21 million, because the inflation rate would still be the same.
If there were 21 trillion coins and they're all mined in 9140, then no, it wouldn't be the same. If they're 21 trillion coins and every other consensus rule was the same with bitcoin then every block would reward 50*1,000,000 for the first 209,999 blocks, 25*1,000,000 for the next 210,000 blocks and it goes on. The market cap wouldn't (probably) change and every coin would cost
current_price / 1,000,000 => 53,000 USD / 1,000,000 = 0.053 cents.
But in order to be mined in 9140 you have to define:
- The reward of each block.
- The average time between mined blocks.
- How often will a halving occur.