Bitcoin is an internet protocol, Ethereum is an internet protocol. Protocols are very sticky. They don't get replace just because something is a bit better. As Peter Thiel says anything new needs to be at least 10x better to stand a chance of competing. read "HOW TO POSITION FOR THE RALLY IN BITCOIN" by Tuur Demeester https://casebitcoin.com/docs/HowToPositionForTheRallyInBitcoin_TuurDemeester.pdf1

side note: It is even questionable whether something can be better than BTC or ETH. What most protocols do is they just choose different set of engineering trade-offs, i.e. they are worse at something and better at something. e.g. Monero has privacy but it has 10x bigger transactions than bitcoin and it has directly un-auditable monetary supply so a risk of an inflation bug.

The development in this space is turbulent and the future of these networks is hard to predict. I would posit that there are non-negligble quantities of BTC (the asset) locked into cold storage not intended for sale in the immediate future, regardless of the development (or lack thereof) of the bitcoin network, BTC willl be around fore some time imo (maybe as a kind of prime collateral), given it could even migrate to a different chain if need be. Ethereum for now has strong moat, and lots of exciting development and as smart contract platform can still accrue a whole lot of value to its network, so also hard to foresee an end in the near future. ETH itself also has multiple value propositions (collateral, staking, consumable for smart contracts). 

For now I feel conviction for their persistence but who knows what the future brings? I'm exploring the idea to rotate some of my holdings into a total crypto market cap coin next cycle. There is now TCAP https://cryptex.finance/1 a smart contract which tracks the total cap using an oracle to bring the data on chain. I guess it has smart contract execution risk and obviously depends on the continued existence of Ethereum, but generally capturing the beta of the space without getting into the alpha weeds seems like an awesome proposition over long term. Any other ideas how one can capture this? think crypto ETF....