Final answer:
The cooling of Earth will likely lead to an expansion of the solid inner core and a reduction of the liquid outer core, with nuclear decay slowing the process.
Step-by-step explanation:
As Earth continues to cool, the most likely outcome is that the solid inner core will become larger and the liquid outer core smaller. This process occurs because the core loses heat to the outer layers via conduction and convection, eventually leading to the solidification of the liquid outer core. The heat generated by nuclear decay in the Earth's interior slows down this cooling process by providing additional energy that keeps the interior molten for a longer period.