Anybody who worries about Trump refusing to leave if he loses. ignores the fact that somebody else wins and becomes President on Jan 20th. Trump becomes a pathetic loser who has had a major psychotic break. Meanwhile the new President is Commander-In-Chief of the Armed Forces, head of the Executive Branch, etc. The Secret Service will protect the President. All they'll do for Mr. Trump is put him on a helicopter ala Nixon. These are professionals with a sworn duty to the Constitution, not Trump.
Everybody in the Executive Branch works for the President, not for Mr. Trump. The only Trump loyalists are people he installed who are unemployed on January 20th.