Ryan Shrout on PCPer has this to say on the stealth announcement:
For those of you worried that GDC would sneak by without any new information for NVIDIA's GeForce fans, Jen-Hsun Huang surprised everyone by showing up at the Epic Games' keynote with Tim Sweeny to hijack it. The result: the first showing of the upcoming GeForce TITAN X based on the upcoming Maxwell GM200 GPU.
JHH stated that it would have a 12GB frame buffer and would included 8 billion transistors! There wasn't much more information than that, but I was promised that the details would be revealed sooner rather than later.
Prior rumors positively identified the 12GB frame buffer, and suggested a $1,349 price point, though this has yet to be confirmed.