If BTC falls we all fall miners, hackers, speculators, hodlers.
But it won't. It went one time to $3 and then up to $1000.
BTC is eventually doomed & will return to 0, but not yet.
Holding is still a gamble (if you ever bought any), you might be asleep when the real crash comes & you wont know until after it has happened.
Other alts will live on, so I hodl those & just keep a few small parts of a btc, hedging reduces risk.
I can't see how bitcoin could fail letting altcoins live on or even prosper. The day bitcoin dies, all alts will die with it (or will have died long before).