It would be helpful to define terms first. Capitalism is the system of private ownership of scarce objects. People are scarce, land is scarce, resources are scarce. Even if energy becomes plentiful, the means of production of that energy will remain scarce (solar panels and other capital goods). Even if you can 3D print any object, the resources used as inputs are still scarce.

In short, scarcity will not go away, although it will continue to get significantly better, as more valuable and useful things can be produced with less (less labor, less energy, less resources, etc). Therefore private ownership and voluntary association, aka capitalism, will remain.