No, i don't think so, because Why do they follow Google. Each search engine has its own strategies, Google doing it in their own way. Thats all.
maybe in the future....as of now, no one can beat Google and it even invades the mobile phone industry....
Even if they do it web masters will not have interest about it as much as Google PR. Because of low usage compared to Google.
I don't think for it may vary with the logarithm they use. Google has unique logarithmic update recently.
I think Yahoo Launched PR Points (Like Google). But i think yahoo launched some thing different than google. That's why delay ...
That will be copy of google. And yahoo does not think pr as a major thing. Same with no follow links. Google does not give any value to nofollow yet yahoo puts value even for a nofollow link.
if yahoo will do the same thing, that will be copying. Every search engine should do different thing am i not right?