Yahoo or Bing have not indicated that there are planning to include Page Rank, maybe Google might frown if they did, claiming it has the patent on it, whatever happens if they did, everyone will know Google beat them to it, and they are just copying them
I think Google dont have much time to spend on PR update this year, they have other much important things to work on this year than the PR update. But I think they are going to work on it before the end of this year.
I think they will update PageRank eventually. Afterall, they could have stopped showing PR in the toolbar if they wanted to at anytime they want.