I will say 1 thing. It would be impossible for Obito to fight Minato with just 1 eye. The risk in doing it would simply be way too high. Making logic over, why he has just 1 eye is wrong. Uchiha Madara also had an eye, when Obito fell to him. We can only be right to assume that Madara trained Obito for this encounter. Madara also said something very important in the latest chapter, and it was that he needed 2 sharingan to unleash his full power. But that was not marked on himself alone, that goes for any Uchiha.
If Obito could have faught that well against Minato with just 1 eye, Kishi would dissapoint me even more. I'm sure he had another eye. Also in case he needed to use Izanagi - for instance. Also Madara might very well have had an eye with a very unique ability. Also don't forget that Obito also hid his other eye, when he fought Konan. I don't think there would be any purpose in hiding his other eye if it was just for the use of Izanagi, since almost no people knew about Izanagi. So there is definitly a secret we are yet to discover.
