I think more depends on how we shape Lorgar's Mythos over time. He's the son of the magician warchief of a desert tribe now, but in a year, he may be the son of an archetechnologist, and the year after next the son of the World Emperor establishing urban civilization fed by vast vertical farms.
I think there could be also huge impacts depending on how else we (can) shape Lorgar. A Lorgar who picks up five dots in Savant and a load of Helltech cyberware is going to be very different to one with five dots in Inheritance (Infernal Half-Caste) alongside the Lidless Demon Eye is going to look pretty different. and different again to one with Elnloghtened Essene and bunch of Martial Arts charms.
While all this is true I do not think Fan Morgal is ever going to stop being a magician, if we do archeology it is going to be with the intercession of the spirits, if we stick hell-tech in him it is going to be hell-tech and if we make him a half-Caste, assuming that can be done... ho boy that is going to be blatantly magical. As far as the Iconoclasts go no changes we make in the future are likely to be as big as the changes we already made IMO.