Will trichomoniasis go away on its own in men?

Usually not: Usually not. It takes a single dose of an antibiotic, so easier enough to treat. Here is some information: http://www.cdc.gov/std/trichomonas/STDFact-Trichomoniasis.htm

It can: This is a known phenomenon. In studies up to 20% of men infected with trichomonas will spontaneously clear the infection within two weeks. Though, I wouldn't rely on this being the case for everyone.