10%.
- Chance he runs for vice president and wins, with the presidential candidate resigning promptly: 5%
- Chance he cancels or significantly delays election: 3%
- Chance he successfully refuses to leave office after election using force: 2%
Here are all the ways that doesn’t happen:
- Chance he dies of natural causes: 70% - it’s about one in three per year for a man in his early 80s, which would give us 1-0.66^4 = 81% for four years, but he has access to the best possible medical care
- Chance he runs for vice president and wins, with the presidential candidate promising to resign promptly, and is betrayed: 10%
- Chance he attempts to cancel or delay the election and fails: 10%
- Chance he refuses to leave office after election and is removed: 10%
These things have a less than 1% chance:
- Constitutional amendment
- Supreme court allows him to run for a third term in violation of the unambiguous text of the constitution
It’s the wording of the 22nd amendment that makes this a possible outcome (emphasis added):
It could have said “no person shall serve as president for more than two terms” or similar wording, but it does not. I agree with you that conservative justices are likely to use this interpretation.