I'd guess that speed is still the issue. Cross platform is going to be an issue isn't it since you don't know what 3d card is available when you write the code? Does java have anything to support auto discovery of 3d capabilities? And I'd guess that there are tools to ease porting a game between the wii, xbox, and ps3, but expensive I'll bet.
The ps3 has java, via the blue ray support. Check the bd-j site.
