I suppose there's a pre-Oculus Rift and a post-Oculus Rift timeline here.
Pre-Oculus Rift, SCE had talked about the future possibility of VR and AR HMDs in a number of contexts. At CES 2009 Sony showed an early prototype of 'see through' glasses for video consumption. They latter, obviously, produced non-optically transmissive HMDs for video consumption in the HMZ line. In 2011 Sony was pushing stereo 3D on PS3,
and the team behind the tools for that revealed they were prototyping VR experiences and were engaged in R&D around tracking for VR (this is a team at Evolution studios, made up of some people with ex military and flight sim backgrounds). Separately, various Sony execs have often predicted AR through a HMD at some point.
Post Oculus Rift, Sony demoed a modified HMZ set with tracking and AR at TGS 2012. Then in September last year,
reports emerged from Eurogamer that Sony was developing a VR HMD, led by the team at Evolution Studios mentioned above. It supposedly was originally planned to have a 2013 reveal, but was pushed back until 2014 to avoid confusing the pre-PS4 launch message. Sony execs - notably Shuhei Yoshida - often addressed questions about Oculus Rift with some subtle and not so subtle reflections on Sony's own R&D capacity and work.
Then later in 2013, several patents started to emerge from SCE, attributed to people at the Evolution team, around HMDs. A little later again, more HMD patents were published from SCEJ, focussed more on AR applications of an optically transmissive HMD.
And that's pretty much where we are now. Basically an awful lot of smoke.