Apparently it was released on may 3, 2012, but at the time it was posted on GIMP.org, the Mac OS X version wasn't up yet. But now:
Now the brand new GIMP 2.8 is also available for Mac OS X (Snow Leopard and Lion)!
The GIMP.org Downloads page still thought it was 2.6 only for Macs, but when I went to
GIMP on OS X, the new GIMP 2.8 was available !!!