‘China wants the lead’ so Xi can be the hero of the hour.... which is why this trip to China first...then Fatboy to S.Korea... and lastly visit with Trump...
I think, for NK, they want to exploit conflict between U.S. and China which is on-going on many issues, getting the best deal out of it.
However, NK may be asked to give up more than it is willing to. That could be a major sticking point.
Xi and Kim did not look upbeat while together. Kim stayed only a day in Beijing. It could be an indication that things did not go smoothly. On the other hand, Kim could have been mindful of what would happen if he is away from Pyongyang for too long.