Yep, I've just discovered the same thing.
The *DID* add stereoscopic mode to GT5 in a patch if I remember correctly, so hopefully they will do that *soon* for GT6, but until then I won't play it anywhere near as much as I would. It will mostly sit in the "waiting for a critical update" bin. (Kind of like GT5 did while I waited for online and offline physics to match-up).