Charlie Demerjian from SemiAccurate claims NVIDIA signed a deal with Globalfoundries, not for GPUs but for Tegra and other ARM-based chips:
After a year or so of negotiations, it looks like Nvidia has finally signed with Global Foundries. The deal is still somewhat shaded in mystery, but it is unlikely to be for GPUs, sources say it is almost assuredly for Tegra and other ARM based chips.
Global Foundries is very tight with ARM, has SOI capabilities, and looks to be ahead of the competition for the next process generation or two. GloFo may be tight on spare 28nm capacity, so Tegra is a perfect fit, low volume and long lead times for any volume shipments.