Doesn't the GTX 460 TDP rise significantly when overclocked? Would opening the disabled areas make it come more in line with performance without consuming more power?
TDP's rise significantly for *any* (AMD or Nvidia) graphics card when the clocks are increased. But there are several big factors you didn't consider:
Compare the gtx465 to gtx470 on anandtech's original gtx465 review. Both are running at the same clock speeds and using the same GF100 chip, however the gtx470 is around 25% faster while only drawing 5% more power in games despite having more of the chip enabled.
The compare a gtx480 to gtx470. More chip enabled, 100mhz higher clock speeds. The gtx480 is around 20% faster while drawing around 15% more power in games.
Now look at the latest reviews for newer manufactured gtx480's - some are running 50mhz faster than standard gtx480's while simultaneously pulling less power than the initial gtx480's at stock speeds.
So, in a nutshell, and especially with binning parts, TDP will be reasonably contained
when, not if, Nvidia releases the 384 shader gf104 part.
EDIT: Further hinting that a new card is imminent is given in the cnet article with the nvidia / AMD emails
http://news.cnet.com/8301-17938_105-20020318-1.html:
"Further to our e-mail last night about the GeForce GTX 460 1GB/GTX 470 price adjustment, please rest assured that our price adjustments are in fact permanent. Any claims that our pricing update is temporary are patently false. The price adjustments we made are not temporary, and are
reflective of an upcoming change in our product lineup."