Three (or more) successful terms has only been done twice (in modern times). Roosevelt to Truman and then Ronald Reagan To GHW Bush in 92'. So, over 70 years it's only been done twice.
But, should Trump win a second term, and I think there is a good chance he might, Haley would be a good candidate to consider. As a women it would be a breath of fresh air and might look like a change, something people want after 8 years.
As side note, those who think Trump won't get reelected only need to look at history. The only two modern day Presidents who were not reelected were Jimmy Carter who had the Iran hostage crisis weighing him down and an incredible political star to run against, Ronald Reagan. And GHW Bush who had to contend with Bill Clinton a consummate politician. Also a third party run by billionaire Ross Perot who received 19% of the vote most of which many feel was taken from Bush.
But, yes I like Haley. She'd have to get through probably 20 competitors to get the nomination but it could be done.