Regardless of what bitcoin's fiat worth is there will always be enough to go around as 1 bitcoin is divisible many, many decimals/values. For this reason I say yes bitcoin will be around in 100 years. The only question is if it is still profitable for miners but I presume it will be, maybe somebody could clarify this.
It could still be profitable to miners. Some of the things I have read state that there will be so many people using and transacting with it that the fees will be really really low, but will make up for it.
It is also possible that if miners drop out or cannot profit the difficulty could go down.
100 years from now though I would Imagine BTC has Hardforked multiple more times and people are using different versions. I think they would just use the BC altcoins and use a service like shapeshift to conver if they need to buy someting from somewhere that doesn't take that BTC altcoin.
the interesting thing is that HF may be useful in decreasing network hashrate. If more and more hashrate goes into other BTC altcoin clones/Hardforks it would be interesting to see how that plays out.
First off, why would you think so far ahead. I mean 100 years is still so far ahead that whatever happenings that would probably take place in the moment in time, won't even have as small as a ripple on what is happening to us now. But to answer the question, I think it can survive, but with the support of the people and the continued dissemination of knowledge, and continued use and patronage of people. If all these factors would converge, it would contribute to the continued existence of bitcoin or cryptocurrency, in general.
