I’m not so sure reunification would be a good thing just now. Both peoples - North and South - are pretty proud.
The carrot that POTUS has been dangling for Kim, is that he can be a great leader for his people, and that the North can be economically strong, etc. etc.
That implies to me that we’re willing to let him remain in power, and table reunification talks for a decade or more.
De-nuclearization, getting rid of any chemical weapons programs they might have, and getting the economy kick-started will be priority for the forseeable future.
At least that’s my take.
The rumor is that he will have a ceremonial role in a united Korea with access to all the booze, drugs and tail he can handle. He'll be lucky to live five years under that regimen.