Ethereum is garnering quite the network effect for itself, but will it scale? The latter is effectively the thing that an Ethereum take over hinges on. After witnessing the Bitcoin scaling debacle, it honestly makes me doubtful of the political issues that come along with the scaling of any cryptocurrency.

Effectively, even though Bitcoin has its issues, I think that it will exist and even thrive over the next 100ish years. A lot can change in that amount of time, but Bitcoin will survive during this time, which is the question posed in the OP. The cryptocurrency "top 10" in market capitalization will look very different in 100 years I am sure....