For the purposes of this question, Xi Jinping's leadership of China includes both formal titles (President, General Secretary, Chairman of the Central Military Commission) as well as his de facto leadership.
If Xi ceases to hold all of his formal titles, but comes up with a new one and is still widely recognized as holding de facto power, this would not count as ceasing to be China's leader.
If Xi becomes ill and arguably "de facto" power is held for a short period by someone else, but Xi keeps any of titles during this period, this would not count as ceasing to be China's leader.
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@JoshuaWilkes I expect this question would resolve NO, since Xi maintains some of his major titles, and I assume would continue to hold onto de facto power.
@cash Tbh, I'm a bit concerned about this. In the scenario I've outlined above, he very likely wouldn't hold onto de facto power.
@JoshuaWilkes I see. I'd be inclined in that case to resolve YES, since in the scenario you describe, although he still has one of his current titles, the title is effectively ceremonial. The spirit of this question is not ceremonial leadership.