NE Asia Online has a very interesting article online exploring Matsushita/Panasonic's push into digital SLRs using the 4/3 system by 2006. Panasonic has previously teamed with Leica for optics, whether this represents a new direction for Panasonic is unknown.
The article notes that Canon has 37% of the digital SLR market; Nikon 24%; Olympus 17%; Pentax 14%; and Konica-Minolta 7%. With most analysts suggesting the compact digital camera market is saturated in Japan (with Panasonic only holding a 3% market share), it's wise for Panasonic to move into a growth area.
According to this MacWorld article, Nikon says that it has 40% of the global DSLR marketshare (thanks to Jayanand Govindaraj for the link).