What I don't understand is why people even keep talking about 120hz.
I would agree that I would prefer displays have 120hz input capability so I can send a 120hz signal from my htpc. I would agree that 120hz is optimal for 3d gaming, as this would give 60hz per eye, typically thought in the gaming community as minimum refresh rate for smooth gaming without eyestrain/headache. There are already 120hz monitors for 3d pc gaming, they've been out for like a year.
But 3d bluray does not need 120hz. 3d blurays as I understand it will have 2x 1080p24 streams, one 1080p24 stream for each eye. (for the most part. I'm sure some 3d titles could come in the future at 30 frames or even 1080i60) So, the display should simply accept a 48hz signal and then do the frame doubling internally. Granted, the 3d player could do this and send a 120hz signal to the display, but its unnecessary in my opinion. I would rather the display do this personally.
3d bluray will not have 120fps or even 60 progressive fps on the disc. Bluray doesn't even support 1080p60: only 1080p24, 1080p30, 1080i60, and 3d bluray does not change this.