Based on Microsoft's track record when it comes to adding new features to Microsoft Office... it's not going to happen until the next major PAID upgrade.
It seems developers' agenda prioritize 2011 version, but serious issues with 2008 will also be attended. See this
I'm not sure if microsoft will support os x's new features added in lion, but I wouldn't discard it either. As for myself, office 2011 (concretely word processor) was a complete deception, I use it just because I need to share my files with windows users. I don't think microsoft will solve slow loading times, sluggish UI or clumsy large files management. I put my hopes in a new iwork release which brings some missing features I need to throw office away.