Finally there is an easy way how to implement Google Authorship in Joomla sites. I created plugin SD Google Authorship, for easy use and quick setup on Joomla site. Its simply working for multiple authors as well.
Plugin is compatible with Joomla 1.5, Joomla 2.5 and Joomla 3.x.
Since plugin version 3.2 it's properly supports K2 extension