PS4 doesn't use OpenGL. No game console I'm aware of has ever used OpenGL. (The PS3 is the closest example, since it used to let you run Linux, so you could run Mesa - but the GPU wasn't accessible to you.) I don't know why people keep claiming that a given console runs OpenGL.
People probably bring it up because you can often use OpenGL on a console, even if it's through a wrapper library instead of supported directly, or even if it's only "OpenGL-like" instead of fully compliant -- which still may be better than porting to the native format depending on the game. (Though the original XBox's D3D was pretty OpenGL friendly: http://www.emuxtras.net/forum/viewtopic.php?f=193&t=4009) So for the PS2, PS3, Wii, and handhelds like the PSP and DS, there are OpenGL or OpenGL-like wrappers available.
Sure, but in practice this is not 'OpenGL' enough to count when talking about OpenGL making ports trivial. (I say this as someone who recently shipped a game w/a OpenGL renderer that has a PS4 port in the works - there are a surprising number of differences!)
The core OpenGL feature set and API factoring are almost certainly things you can expect to be similar on console platforms, at least where the hardware matches. So in that sense 'It's OpenGL' is almost true!
