First of all, Im not even convinced Iggy will be dead by 2400 as hes already 300 years old, so hes probably got a while left yet. If, unfortunately, he does meet his demise at some point in the next 387 years, then it probably won't even be necessary to digitally regenerate him. I reckon that when they finally find his skull his hair will still be attached, thicker than ever, and the rest of his skeleton will pretty much resemble his ever-bare torso as it is now. Hell just look even more hungry than normal. When his face appears on the screen, hell almost definitely look like he does in those insurance adverts, giving the anonymous future the great privilege of being exposed to the face of a great man who even manages to make selling out look absurdly cool. The only downside to this is that when our society is completely misrepresented as a community of reptile-like, gender-confused rockers, the creepy little marionette version of Iggy also found in the adverts will inevitably be cruelly laughing at us as it burns in hell for eternity.