Assuming he doesn’t change the rules and appoint himself president forever, then the limit is 2 terms, consecutive or not.

Even if a person started their presidential mandate partway through a 4 year cycle (as happened after Nixon stepped down and after Kennedy was shot), it’s still 2 terms, not necessarily 8 years.

If Trump dies in the next 4 years, Vance could serve out the current term and would only be eligible to become president for one additional term.