Well some analysts have stated it was a long term plan, to use the latter part of his appearing on television (The Apprentice) to before pushing to try to be the GOP candidate. Keeping that aside you are right, he has not shown any worrying signs of trying to hold on to power beyond by underhand tactics.
What about another scenario, maybe a bit too realistic. If he thought he was going to lose the election in November 2020 or if he won re-election but say two or three years in to his final term - would you put it past him to start a war either by provoking any state (so-called enemy state or other) in to taking action or simply by taking action himself by attacking another country?
Any such scenario could invoke a Franklin D. Roosevelt style of remaining in office for the duration of the war and beyond so would Trump be tempted to go down that line?
Why though?
I don't think he is power hungry like that or he would have been trying to get into the Gov for a long time, which he hasn't..