It looks like Nvidia is gearing up to launch a pair of 600 Series mobile graphics chips. We know this because somebody went and dissected Nvidia's recently released GeForce 283.38 drivers and found a couple of lines of code referencing the unreleased parts, which is a good indicator that they'll be showing up soon.
VR-Zone dug up the following lines of code from the new drivers:
Not much is known about these upcoming parts, though VR-Zone surmises it's entirely possible the GT 630M could be the shipping name for Nvidia's GK107, a part that features a 128-bit memory interface and supports DDR3 and GDDR5 memory. The GK107 is Nvidia's first chip based on its next generation Kepler architecture.