Hello Donder, I dont see that happening for a few reasons:
1. They are going to use those B767s on Asian routes which are doing good for them, for example to Taiwan, Japan or Korea.
2. There won't be too much people travelling between SGN-LON. (I may be wrong here just my assumptions)
3. If they want to start new intercontinental routes, I would think they would fly to Moscow as planned, but maybe without a stop in Beijing unlike when using the A320/A321. But they are aiming to win 5th freedom rights on PEK-Moscow (which airport in Moscow did they use to serve?)