Reaching 10 GHz for a CPU will never be done in silicon.

It could be done if either silicon will be replaced with another semiconductor or semiconductors will be replaced with something else for making logical gates, e.g. with organic molecules, to be able to design a logical gate atom by atom.

For the first variant, i.e. replacing silicon with another semiconductor, research is fairly advanced, but this would increase the fabrication cost so it will be done only when any methods for further improvements of silicon integrated circuits will become ineffective or too expensive, which is unlikely to happen earlier than a decade from now.