proportionality of space to transistor isnt relevant to power density. More transistors per unit area is, irrespective of proportionality. All die shrinks since increase transistors per unit area will increase power density. See definition in bold below.
I know you are crusading against trigate, but it isnt going away, since some experts, including intel think currently necessary to continue moores law in an economical fashion...until better technologies arrive.
And honestly not interested in continuing a discussion of trigate, when I can read factual information from credible engineering articles if interested.
Power density
http://arstechnica.com/old/content/2007/01/8716.ars
http://www.anandtech.com/show/4313/...nm-3d-trigate-transistors-shipping-in-2h-2011