Physical immortality surely does not mean a fresh imprisonment to one particular form. The supramental being will be free to leave aside the body and switch over to another without any loss of consciousness as happens now following the process of death. In all likelihood it would have found the occult means to create a new body for itself and switch over to it. This is the general drift. However there is another aspect of physical immortality that we need to understand. Nonsense or not it is only when we are able to not only prolong life at will, to keep the body free from all disease and disintegration and eventually help it to escape from the law of death can we say that there is a complete conquest over all the forces of darkness that right now govern material existence. Once this conquest is established then the rest is a matter of method and means that the New Being will use. However if the conquest over all the material forces that weave our bodily life are not conquered then whatever process we may use will remain precarious since earthly body will remain susceptible to death. It will be in that case a partial and incomplete victory. Or else we will have to rest content with a partially supramentalised body, like the ethereal body that does not decay in certain tantric traditions notably the chinmaya body that Vaishnavas speak of or the body of Light. That however is different from the supramental body which will the sign of the complete conquest of the Divine over matter using our humanity as a fulcrum.