Depends. Ever hear of quantum computing? The physical size of the thingie might be limited (it should be big enough to see, I guess), but there could be millions of processors on a "chip."
--Boris
Package sizes are determined by economics, thermodynamics and memory bandwidth, and not just by device size.
We have separate processor IC's, circuit boards, racks, cabinets and rooms because it's practical for different companies to compete at a given size, to depend on separate providers from the next smaller size, and sell to markets for the next larger size. This depends on the cost of integration of packages of one size into a package of the next size being fairly cheap.
I just don't see wide spread use of low cost means to integrate pin-head size quantum CPU's into a single I.C., across corporate boundaries.
And except for specialized programs requiring very regular parallel operations, putting thousands or millions of CPUs into a single I.C. is useless, because you can't get the data in and out -- memory bandwidth will be limited by the cross I.C. interconnect technology.
I don't know enough about quantum computers to know if they will run dramatically cooler - if they do then at least the thermodynamic hurdles for such a beast will be less.
Device size reductions have ruled the development of computers for a half century now, known to many as Moore's Law.
Nothing grows (or shrinks ;) at the rate computer device sizes have been shrinking forever. The delightful insanity of the last half century will end.