a) Bonds is an asshole, which means that his defenders will use his attitude as the reason the accusations persisit and will provide for reason enough that Bonds will never be forthcoming about what he was doing with Anderson and BALCO.
b) We won't know for sure untill he dies/doesn't die in the next 10 years of massive kidney failure. Even then, his supporters will say that nothing is conclusive, like how you don't know which cigarette it is that causes lung cancer.