Yeah, I agree with mordko. The generals are always fighting the last war.
When it comes down to it, investing is really about predicting the future. Because no one can do that with total accuracy, you just have to play your probabilities.
What I would be curious about, and maybe something j4b could do the calcs on, is what is the current ceiling on bonds? How much would your bonds have to rise to reach a YTM of zero? I know bonds in Europe and Japan reached below zero yields, but lets ignore that for now.