Why should Sony pay millions to get the rights to a weak franchise? Shenmue didn't help sell Dreamcast consoles (even with its million in sales). It certainly didn't do well on XBOX (dropping down to only 300,000 sold compared ot its predecessor). And frankly, it is little more than an afterthought in the mind of Sega fans and 'what if' hardcore fans who remember the days of the Dreamcast.
What could it possibly hope to benefit going to the PS3 aside from some dry hype and hopefully selling to some Sega fans....which are mostly buying Wii games?