I guess the best answer to that question is of course a BIG NO! Granted, China is a big contributor for the rise and adoption of Bitcoin and they are primarily the country involved with Bitcoin mining due to very cheap electricity cost.
Now, the Chinese government has its own agenda and I think in the long run Bitcoin can be running against those agenda so they are now thinking of slowly disengaging and disconnecting their citizens away from the cryptocurrency platform.
I know that whatever China will decide on the impact can be heavy on the market and this is shown with the recent decision banning the ICO projects and the unconfirmed total ban of Bitcoin exchanges though it is still a rumor and nobody would want to confirm.
Can cryptocurrency still go on and have a very optimistic future even without China as part of the equation?
I agree in this argument. Yes for sure it will affect the Bitcoin performance in a negative way. But that does not mean that Bitcoin will die. In my opinion, Bitcoin will drop to lower price again way the same as 5 years ago. However, this is an opportunity to invest again in Bitcoin at lower price and there is a big chance for the price to come back or even higher than today.
What will greatly affect affect Bitcoin than China is the Korea because there are rumors that the government is planning to ban Bitcoin.