The two term limit was set by the 22nd amendment to the U.S. Constitution. The language in it is that no person may be elected to the office of President for more than two terms. It does not specify any criteria about consecutive terms, meaning it doesn't matter. They simply can't be elected more than twice to the office President under any conditions. It also specifies that if they served more than two years as President when they weren't elected to that office (such as when a VP assumes the office after the President dies), they can't be elected to the office of President more than once. In other words, a 2+ year term of a president after succeeding the previous president whose term ends early, counts as a full term in regard to this 2 term limit.
In other words, this SHOULD be his last term. There are two legal loopholes, however. 1) If he somehow managed to coerce a skip or elimination of the next election, he could assume another term without defying the constitution. There is currently no mechanism to do that, but an act of a partisan Congress upheld by the partisan Supreme Court could make such a thing possible. 2) if he ran as VP for another person, which is constitutionally allowed, he could be elected as VP and then the elected President could resign, die, or be removed from office and Trump would be President again. Also, a new amendment to the constitution could be passed to negate or modify the 22nd amendments' term limit. Though that would require a lot of Democrats also voting for it.