I have a feeling something is not right here... Obito is going to loose control very soon, he's barely hanging on to the Juubi, yeah he gain a little control now, but watch when it reaches it final form inside of him. all hell will break loose
it looks more like rinnegan when compared to minatos arm but did you notice the dark triagular shape on the bottom left side of it and that there are 9 small tomoes on his back. for me it looks like the 10th tomoe (10 tails) with a rinnegan in the middle