Apple has released Digital Camera RAW Compatibility Update 6.04. The update adds RAW image support to Mac OS X Yosemite for 18 new cameras from Canon, Fujifilm, Hasselblad, Leica, and Nikon.
The update is a 7.7MB download. You can upgrade via the Updates tab at the Mac App Store. Digital Camera RAW Compatibility Update 6.04 requires Mac OS X 10.10 or higher and iPhoto 9.6 or Aperture 3.6.