I agree with Vitalik, it's impossible for Ethereum to hit zero. I also bet that if there wasn't this downtrend, people wouldn't even have even thought about this possibility because it doesn't make sense. How could a strong project, that is used by most of the community for ICO's  and has a current a marketcap of 21.7 Billion Dollars just go to 0 ? It just doesn't make sense.