"This new processor stems from a strategic partnership, also announced today, in which NVIDIA has obtained rights to develop its own high performance CPU cores based on ARM's future processor architecture. In addition, NVIDIA licensed ARM's current Cortex™-A15 processor for its future-generation Tegra® mobile processors."

"ARM's future processor architecture" sounds like something secret and yet undisclosed, even from ARM.

It's also distinguished from the latest official developments publicly known from ARM, the Cortex-A15 (which is also in the future).

So it's something different. Whether it's "ARM64" remains to be seen...