To understand 10-bit color vs 8-bit color, see 30-bit Color Support in OS X El Capitan with Dual NEC Wide Gamut Display + 32-bit Color.
Hooray! After many years, finally here in late 2015, 10-bit color is available on OS X El Capitan, and now Adobe Photoshop CC 2015 supports 10-bit color in the latest update.
In a cruel twist for my work, 10-bit color requires that GPU support be enabled—but enabling GPU support yields blurred images in Fit on Screen mode on a 2560 X 1600 display with most of the image sizes I process. So I either get blurred images with 10-bit color, or sharp images with 8-bit color. Gah!