He will. And I suspect it will be shortly (within the first two years) after he takes office, putting J.D. Stalin in charge. I suspect he has a serious illness, of which both he and his close advisors are aware, and they are keeping silent about it. It would explain Vance's presidential-nominee-style campaigning as well as a few other things about the planned transition...
That should actually make people more scared. A narcissist cannot fully comprehend their own death. Instead, it will make him even more volatile, more violent, and more vicious. If a narcissist is going to die, they truly believe everyone and everything else should too. Ask anyone that has watched a narcissistic parent die.
A narcissist faced with a terminal diagnosis is likely to respond with intense emotional volatility. The sudden loss of control and the threat to their inflated self-image can ignite unpredictable bouts of anger and even violence. Their sense of entitlement and the belief that they deserve special treatment will cause them to lash out anyone that does not meet their demands. This rage, driven by a deep fear of losing control, can manifest in dangerous, hostile outbursts as they struggle to maintain dominance in an increasingly powerless situation.
Simultaneously, their manipulative tendencies may escalate. They weaponize everything. It they're dying, everyone should be dying. The narcissist's desperate need to protect their fragile sense of superiority leads to highly destructive behavior. So, if it's the case that he has received a terminal diagnosis and he wins the presidency, which polls show is increasingly likely... Strap. The. Fuck. In.