I wouldn't want Jony Ive's new job
1) The HI team might have been fiercely loyal to Scott Forstall and think Ive is the reason Forstall got the boot. Also they might be partial to the whole skeuomrphic design language and not very receptive to change, especially coming from a hardware designer.
2) Any minimalism Ive attempts to introduce will be immediately compared to Windows and Android with cries that Apple is ripping them off.
I suspect Ive is up to the challenge (otherwise Cook would not have given him this promo) but I think it will be a big challenge and something that will take years to implement.