Apple next year will be moving away from Retina (right now the 13" are using the old stock of retintas from last year to just get rid of them) before they introduce IGZO... so everyone is buying old retina with haswell. Have to get rid of old stock of displays to cut down the money loss.
It is more likely the process of laminating the glass onto the panel, or some stage of manufacture, that causes the yellow tint - not the screen itself. Hence why there are cases of yellowing on all LG and Samsung screen types.
There is nothing to suggest IGZO displays will solve the problem. The Retina iPad mini has an IGZO display and has yellowing issues too.