Always keep calm and look to the important things
It's been a little bit studied before, but by somewhere between 2030 to 2040 all bitcoin has been practically mined, or close to 99%. The number would be above 20 million but below 21 million, and in fact it will never reach 21 million. Forecasted is something like 20.99 million. The last and final million coins will then take a literal one hundred years.
Actually, by 2024 we have 20.343 million coins, only 96% but still that's the mark.
By 2036 we have 20.917 million coins, about 99.61%.
By 2064 we have 20.999 million coins, 99.99% and then several decades of block rewards below 0.003 BTC per block (and getting smaller), not including transaction fees. It's likely by this point that transaction fees will equal or exceed the coinbase reward by this time, maybe even earlier.
Between 2036 to 2064 or about less than 30 years, the network will mine less than 820k new coins. Then between 2064 to 2140 less than 10k new coins, spread out over several decades.
We don't need to wait until 2099 or 2140 or the "last bitcoin", we'll start seeing stuff happen waaaay before then.
So, just to clarify, technically, not all bitcoin will be mined until a hundred years from now, but practically, you can think of it as already mined within the next couple of decades.