The heat produced in a traditional data center is already unwanted and wasted and takes a ton of electricity and machinery to get rid of. Given that processors like to operate around 50 C, that's not a lot of heat to preserve and transport and do something useful with.
The issue is more that transistors will always generate some heat- making the threshold higher / being more efficient doesn't solve the fact that there's still some waste thermal energy that needs to be removed.
Modern transistors are rather small and would desintegrate at too high temperatures. Not much you can do about it at those scales, any material will decompose.
