It's not going to vanish. It's had so much cash pumped into it, and so many projects are being built on top of it, it'll just die a lingering death rather than vanish.
It always surprises me how fast people lose faith in the market or in the different coins that we are part of the community, ethereum is the second strongest coin and it's only behind bitcoin in terms of popularity and market cap and yet some people think that it is going to disappear in a sudden way, something that is impossible, if ethereum were to disappear we will see it slowly falling out of its position as the second most popular coin.
I think altcoin developers from erc20 tokens are not stupid and if ethereum will die or disappear, then some of them will definitely move their tokens from the ethereun platform to other platforms. But we don't see that and all remain on the ethereum platform.