Obviously, Donald Trump won't be impeached or removed so long as the Republicans hold even one House of Congress. And even should they lose both in November of 2018, launching an impeachment - as the Republicans discovered with Bill Clinton - is very dangerous to the impeaching party. Unless you have a highly credible set of extremely damning facts, you turn a constitutional crisis into a political crisis. You rally potential supporters of the impeached president to him. You make his base bigger. So I imagine that he is likely to serve out the full term.