I'm in exactly the same situation.
Brand new Panasonic 65VT50
Onkyo 805 AVR (that I have no intention of replacing)\
PS3 (that I have no intention of replacing)
Here are the options to get 3D audio/video I seem to have been able to discern from reading the forums.
1. Run HDMI from the PS3 to the TV. Run optical from the PS3 to the AVR.
The limitations here are that I won't get the full lossless linear PCM stream I am used to sending to the AVR form the PS3. As a result I normally wouldn't leave it hooked up this way for non-3D movies which means moving cables around to watch 3D. This leaves me to solution 2.
2. Run an HDMI switcher (with one output going to the AVR for normal non-3D audio/video switching and the other going directly to the TV for 3D viewing) so that when I do what I describe in option 1, I at least don't have to move cables around and can get full lossless audio for non-3D content. However, I am not sure what switcher will handle this properly. Any 3D compatible switcher?
3. Find an HDMI splitter that will pass 3D Video to the TV and 1.3 lossless audio to the AVR. This splitter does not seem to exist.
Am I missing anything?