Pregnancy prevention is not the issue, it's STI transmission that must be prevented, especially in africa.

I doubt we will have a viable substitute for a latex barrier in that regard until some sort of pathogen-hunting nanotechnology becomes mainstream. By that point we may well have transcended our present notions of sex/gender altogether.

With regard to pregnancy prevention for men, there has indeed been recent innovation in this area: http://www.theregister.co.uk/2011/06/06/male_pill_boffinry/