Bitcoin will not drop to zero over night, but eventually it could happen when fees rise too much and when the network gets congested again just like it happened before in the past.
Bitcoin Cash is the original 'Bitcoin' and the upcoming tension will be interesting.
It could fall 99% over a week. Going to zero overnight is bit of a stretch. There are way too many zealots in BTC community. Personally I think it is more likely to fall like Ancient Rome, British Empire or modern Sweden. BTC is more likely to end with a whimper but either way trash is trash, end is end. Some idiots loading up BTC because it's the talk of the media is going to keep prices high.
One think BTC wouldn't reach is a $100 billion market cap.
Network is congested right now. It already takes bigger fees to get a Bitcoin transaction through than it does with Bitcoin Cash.
BCash is an empty truck claiming to be faster
Even though we had a steep Bitcoin price drop after the Bitcoin Cash hard fork, I'm sure you're still right today! Bitcoin cannot go to zero because too many people believe in its value. Over the past year Bitcoin went down, sure, but it will stabilize in 2019. With more implementations for Bitcoin payments, more people will get involved and more people will buy and trade Bitcoins.
https://www.hardforking.com/can-bitcoin-go-to-zero/