51% is what we are really talking about, right?

China cannot destroy Bitcoin but it could damage is, we suppose. But why would they anyway? Surely this would be like killing the Golden Goose...

In time with the difficulty rise, it will be difficult for some to continue mining if they pay for electricity, may mining rigs on that note run on Hydropower and reusable resources so this is of little concern.

No one really knows the future of Bitcoin or the Altcoins, perhaps China may switch to other Cryptos if BTC mining becomes unprofitable?