There is already a sound argument in favor of a third run (I will summarize). The point is that Trump is running for a specific office. Previously, his office was "the 45th President of the United States." He was clearly entitled to a second term as "45th President." The Biden term (46th President) intervened. Now, Trump holds the office of 47th President. To which he is constitutionally entitled to run for a second term.

This matches the practice in many states (e.g., for governor) where there are limits on successive terms, but no restriction on running for office again after an interval, whereupon the 2nd term limit applies anew.