If bitcoin dies , Zcash will up and running the show. It's just a matter of switching to an alt coin.
For sure everyone will have to migrate to another coin to continue but it is probably hard to believe if bitcoin really dies, what about the people holding thousands of bitcoins in their wallets and what about the ones running exchanges and other websites with bitcoins? They would surely cry all day and then move towards something else.
According to me it would never happen because bitcoins are now blood of online business. Most of the sites are running only on bitcoin payment system, any problem to bitcoin might lead to big disasters.
Still if this happen many people lost their business and it would result to biggest loss in the history of online business.