As with any scaling, whether empirical or theoretical, it will have physical bounds. The I^4.7 scaling is very good but other than the effects mentioned above governing factors like the inductance of the circuit and so the rise time. If the peak current is increased much more the pinch forces on the conductors will create stresses beyond that any material can withstand. Also the Ohmic heating of the thin skin in which the current flows becomes an issue, causing differential thermal expansion and further material stresses.
