How this can YES:

• Xi dies and his son takes over by due date

• Anything else happens and an official PRC media organ such as CCTV or China Daily issues announcements stating that this person is the next leader

• So the big picture is: by end date, has he been in charge or has he been officially acknowledged as in charge or on the way to being in charge in the future.

Levels

• He doesn't have to have any specific named position, and he doesn't even have to be known as the top person at the start; he may say serve as a general for a year, a provincial mayor for some time, etc. but it can still YES as soon as he's known as the successor. Not a rumored potential successor, but as the person who's planned to succeed Xi after he dies/retires/leaves. Note that even when there is a successor it's not a thing that's often spoken of in official media

Announcements:

• can't be immediately retracted or disappear; they have to be 'active' for 24h at least.

• If the site / source is down or destroyed, the announcement doesn't count as 'active'

• If copies of it float around that's irrelevant.

Media

• Generally we go by PRC official media; situations where someone is in charge but has no media operation are not covered.

Timing

• This can YES early if there's an announcement or takeover etc.

• But it can't NO early because who knows how many sons Xi has.