No one really know how and when its going to happen, to be frank! China didn't yet announced anything about it! They have just indicated their interest on it and nothing else. There are a number of articles which talks about this matter. You can visit the below links,
https://cointelegraph.com/news/china-to-be-first-to-launch-digital-currency-says-think-tank-exec
https://qz.com/1747988/pbocs-digital-currency-has-yet-to-launch-bank-warns-of-frauds/
https://www.reuters.com/article/us-china-markets-digital-currency/chinas-digital-currency-not-seeking-full-control-of-individuals-details-central-bank-official-idUSKBN1XM0H2
Hope this helps!
It seems they are very serious in launching their own coin, and they did not set up a time table and they want to meet requirements, they are looking at the right time to launch their own coin, and of course, nobody can stop or oppose them just like what Facebook suffered in the hands of the congress, honestly it's much more interesting to see China launching their own coin than Facebook coin.