if bitcoin switch to a new algorithm, what will happen toall the chinese miner?
That depends. There's no definite answer to that question.
also this need a hard fork right? chinese will never agree on this hard fork, they would lost millions
Correct, such a change does require a hard fork. The "chinese" (as in the miners located in China) don't have to agree on anything (the other option carries the loss of everything anyways). It seems like some think that these guys have control over the network. People need to stop panicking when they hear the words 'quantum computers'.
Qunatum computers are like unicorns. Everyone knows they exists but noone saw them.
Just because you haven't seen them, that does not mean that you should make such hasty generalizations.
it support encryption for wallet
That's a whole different story. Besides, in order to be able to do something about wallet encryption they'd have to gain access to your wallet file.
