I think a failure in Bitcoin will cause loss of faith in Blockchain technology as an 'immutable, decentralized record keeping system'. Pretty much the foundation on which every other crypto is based. Right now, there is an intimate link between the crypto market and what Bitcoin does as any gains made in cryptos is cashed out/stored via Bitcoin. It seems to be the default coin..almost like crypto gold. Ethereum may well take over in market cap but as a store of wealth, I think Bitcoin will reign supreme. Ethereum will run applications on it which are currency agnostic, whose to say that most of the apps run on it won't be Bitcoin based? :-)
If Bitcoin tanks for some reason, I think this loss of faith will be significant but probably recoverable. Now we have a taste of what's possible this technological concept won't be given up on so easily.
Look at the hard fork Ethereum went through, you might have been forgiven for thinking when that happened that would be the end of that but look at them now, now both Ethereum Classic and Ethereum are thriving.