Green’s Dictionary of Slang

1. (US campus) an unattractive man.

1979		Eble Campus Sl. Mar. 3: future – an unattractive male (it will be a long time before he is handsome): There’s a future for you.
1996		Eble Sl. and Sociability 59: Nevertheless, pejoration has affected some items of college slang. A future is ‘an unattractive male’.

2. the male genitals.

1989

J. Morton Lowspeak 62: Future – the testicles. A common graffitti in mens’ public lavatories is: ‘The future of Britain is in your hands’.