If the hashing algorithm were to change, what would happen, would the blockchain be forked from that moment on? Or will the miners using the new algorithm generate orphans until more than half the hashing power has updated?
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Unlike the debacle back in April, what would happen is a future time/block would be decided to implement the changes.
Up to that point everyone is on the same chain.
At that port it forks, and everyone who hasn't updated will be on one fork while everyone who has updated will be on the other fork.
What actually happens next ... well that depends on the % of who decides what.
I guess those with asics and the security problem may stay on their risk fork and everyone else will be on the new fork.
Though if asics are most of the network by then and they want to keep the security risk, I guess BTC stays a security risk - bye bye BTC