This graphs shows the Market Share variations between 2006 and 2008. The first thing you note is that Canon lost a lot of terrain. Sony and Nikon are doing very well. Olympus loosed 1% Marketshare and Panasonic gained 1%.
I believe Olympus and Panasonic will both gain a little Market Share in 2009 and 2010. Things are may getting worse for Pentax and Canon. And 2010 could be a successfully year for Sony.
More infos are available at photoscala