It depends on the nature of the quantization of the gravitational field. If we expect the gravitational field itself to be quantized in a manner somewhat simila

It depends on the nature of the quantization of the gravitational field. If we expect the gravitational field itself to be quantized in a manner somewhat similar to the electromagnetic field, we may be able to detect quantum effects without the objects being particularly small. A good analogue is the photoelectric effect, which involves no superposition at all and can be observed even with macro amounts of energy involved.