I feel a GT5 release date in June is plausible for the reasons i've been saying for a few weeks now.
The 3DTVS are definitely being launched in June as i've already spoken to my local Sony centre. Now think about it, here we have a company that produces 3DTVS, PS3, who also have the killer 3D title called GT5. Surely wouldn't it make perfect business sense to release these at the same time. The reason being is GT5 will showcase what the PS3, 3DTVS are capable of thus resulting in an increase of sales of the PS3, TVs, GT5.
I honestly believe come E3, MS will wish they never bothered turning up. Just imagine the Sony presentation if they showcase GT5 being played in 3D and they then announce it will be released in a few weeks time!