I really do not think that bitcoin can stay alive after 100 years, because digital technology is constantly progressing and I do not think the great advances that are to come can forgive any of the current technologies that humans have developed until now. It is sufficient to see how far we have progressed in comparison with the previous hundred years, in order to make an approximate projection of the world so different that it is to come, and if perhaps bitcoin survived, it would only be like a rustic antiquity treasured by some collectors.
You are wrong. Bitcoin will be here in 100 years, because it is on the blockchain, which will continue evolving, but Bitcoin will always be there (it does not simply disappear).
With that said, the real question here is will we use Bitcoin in 100 years? (not us obviously, but our descendants)
My opinion is that at least some will. Crypto is evolving very rapidly and there may be a coin that has far superior technology in the future and overtakes Bitcoin.