nVidia never set, announced, or published any dates. Anything we've seen have been guestimations.
People over at nvnews have been speculating March next year. That's based on just as much information.
They know about as much as any1 else does.
Regarding the supposed TSMC's 40nm fabrication issues - they're banging out 28nm for Ti. TSMC's financial figures looked pretty good too.
I have a feeling that the graphic manufacturer's issues in terms of supply are more contractual than anything else.