sallyxi: If you really compare C++ and Java, you will see that Java is much easier to handle in some cases(less hacking, more engineering). But anyway for 3D, you are absolutly correct. But as Duke told us there are ways like JOGL, so OpenGL runs natively and there isn't such a huge performance issue.
Anyway, I don't really see that difficult problems, that we really should port all over to java. That's a big step. And we may solve the problems easier.