The horizon of 100-200 years has already been described here, but one cannot but aggravate this discourse and look into the most distant future.
Judging by what is amenable to our observations, the human body can adapt to different conditions (for example, we see racial differences due to the environment), but adaptation is too slow.
Meanwhile, life in the universe exists in a very thin and unstable film, and literally balances on the edge. And this balance is not eternal. For a very long time before the cooling of the Sun, the Earth will cease to be suitable for life, and no evolutionary mechanisms (in the usual sense of the word) will help humanity to survive in changing conditions (importantly, on Earth or somewhere else).
That is why we have the mind and the will to study the structure of our bodies, their functioning, and the study of our mind itself, in order to make (preferably preserving memory) a qualitative transition to some other form of life.
It seems to me that this is not something that is possible, but inevitable. People are already using pacemakers, artificial hearts and so on. Although, some have learned how to grow - In 100-200 years, the change of organs will be as commonplace as the change of teeth for crowns and prostheses. How could anyone have imagined 100 years ago that people could get beautiful teeth so quickly and relatively cheaply? Now that's the norm.