Obviously I trust in bitcoin however we cannot minimize the risks we are incurring by holding bitcoin, lets take some of the questions you ask as an example, will bitcoin still exist 100 years in the future? I think the answer to that is yes, but will it retain its value or even increase it after 100 years? This is something I do not know, what if during the next decades a new coin that is many times better than bitcoin appears and that is the coin that gets widely adopted by the world and not bitcoin?
And just as gold can be lost bitcoin can be lost just as easily, there are many horror stories about lost and broken hard drives, people that lost the piece of paper were they wrote their seed words or their paper wallets, all in all bitcoin is a great way to store your money but it is still subject to many of the same issues.
I think if you buy now, the answer is definitely no. unless you have unlimited money, you can buy it and keep it until any time. and that won't guarantee anything.
Apart from bitcoin, maybe in my opinion gold can be used as a good reserve asset, because the supply of gold in the world is decreasing day by day. The point is back again to the calculation in terms of managing assets owned. because even if someone owns any amount of bitcoins, it's still useless if you don't know what to do with it.
so not only armed with capital and intention, but knowledge in managing assets must also be improved. small examples in the family are the same. and not much different.