Guys 78 and obese.
There's extreme wealth paying for the best medical care, but unless they're replacing his heart for that of a lizards, I don't think the guy will actually make it through the term at peak health. I think slowly the executive branches and bureaucracy will run the entire state with Trump barely being involved.
The biggest threat to the US right now is that Trump barely understands anything political. According to reports after his first defeat, the CIA, FBI and other organizations had to alter their briefings to the president heavily when Trump was in power as the man simply was not interested in reading a typical report. According to the CIA a "report had to be written as if it was a story, with a narrative, a hook and a reason we "won". The president only read reports in which he was named in. He always had to be a reason we got it done, even if it was made up."
He's a man child. He will be easily manipulated by those around him and his tech bro oligarchs aren't even in a real position of power, they're just in ceremonial advisory positions.
The system always wins, but he will nail a few tax breaks for his backers.