I saw that too but as well my temps and gpu core stay at the highest level and never ramp down to the idle states. I only hope there will be a new MacPro with a kepler card and then things should be a little clearer.
I have a Kepler card myself and I was hoping, too, that sooner or later Apple would have a Mac with a desktop Kepler card. Well, fat chance now... So, I started to experiement a bit and if I'm not mistaken I have good news about power management for Kepler.
First, I tried to get power management working, patching the Info.plist in AppleGraphicsPowerManagement.kext. I got to the point where OS X recognised my card, and loaded the section I wanted, i.e. system.log had an entry like this on boot:
kernel: [AGPM Controller] build GPUDict by Vendor10deDevice1189
For the actual content I tried variations based on the GTX 680M and similar cards Apple has details on. Unfortunately, I never saw any entries in the logfile about OS X trying to switch power states. So, clearly something wasn't working. At the same time though, my system is very quiet and I'm pretty sure that if the GPU was running at full clock I would be able to hear the GPU fan over the rest. I didn't.
Next, I thought that this is about power management and therefore changes would also be observable with a power meter on the wall. I plugged that in and measured a couple of things: idle power consumption, power consumption while playing 1080p in Youtube (Firefox), running the OpenGL test in Cinebench. Readings are averaged. I repeated this with AGPM not building a GPUDict, i.e. AGPM unknownPlatform, and, as a control, the same thing on Windows 7, which presumably has fully working power management. Results:
idle youtube cinebench
AGPM with GPUDict 59W ~64W ~130W
AGPM unknown platform 59W ~64W ~130W
Windows 7 59W ~64W ~130W
I also checked whether the system returned to the measured idle power consumption after running Cinebench. It did. If I read this right then we don't have to do anything at all to get power management working for Desktop Kepler cards, right?
Unfortunately, there is a fly in the ointment, though. The Cinebench result under OS X (in both configurations) is 48fps, while on Windows it's 62fps. Does that mean the card doesn't ramp up properly under OS X? But why the increased power consumption? Which is identical to the Windows one?