Big if. Real systems interact with their environment, which means every psi calculation is approximate, as there is no limit to the possible expansion of domain the wave function is defined on. If we want full description, we end up with the necessity to work with wave function of the whole universe. This means that argument for non-existence of simultaneous values of conjugates does not work. This was after all analyzed by EPR and Bell and the result is, conjugate pairs may simultaneously exist in non-local theories.