I wonder when we'll start seeing CPUs with integrated heat pumps. Stacking a Peltier junction as a layer could start to make sense. Or even having (non-conductive) fluidic cooling. (Although you have to be careful designing the chip or else capacitive effects can cause problems)

Also, we currently have a heat ceiling on the order of 10s of watts. An integrated liquid-cooled heat sink could drastically up that, at least for server-like applications.