Or we could just render the satisfaction of owning an object, rather than actually producing the object itself. (One possibility of the whole singularity thing - desire for physical objects may not be satisfied when we lack a physical existence. (For some value of singularity.))
Well, there's work to be done (quite literally), so unless we discover the laws of thermodynamics don't work, energy will always be expended.
Not if you can set up a framework where physical objects are equivalent to reversible computations (and hence energyless).