Physical limits will be reached, but are already being worked around in different ways. This is also typical of the type of communication used (electrons in metal).

Photons are actually much more efficient for communication (which is basically why we are replacing all existing coper lines with optic fiber). There are already working prototypes of these kinds of designs and i think a working prototype "cpu". Still requires a lot of engineering but i don't think we'll ever reach "we cannot improve this anymore ever".