Considering how long it would take to simply fulfill China's yawning need for large transports, I think China would be more than happy to accept this arrangement.
To note: China has not even made attempt to sell Flankers.
And when such times is reached that China has basically fulfilled her own needs - 200 pieces conservatively - I am sure WS-20 will be ready. If not, China at least two other high bypass turbofan project, I am sure they can pick one.
The problem is more that the market for large transport simply isn't that large, and most of which locked up in countries which won't buy Chinese aircrafts anyway.