Well, 10.6.5 does make Apple's OpenGL implementation a bit faster, but it is still OpenGL 2.1. They have 95% of OpenGL 3.0 support finished, but don't seem to want to switch from GLSL 1.2, so that is still the missing piece.
As for OGL 4.0, there really is no need. Only one card (the G400-series) supports the features of OGL 4 and there are zero apps that support it.