Why would madara need the other rinnegan?
Izanagi makes you lose your eyesight in one eye homie
Are we sure it does when it is used with Rinnegan and Hashirama DNA?
It would make sense as to why Tobi has been keeping that other Rinnengan plot-wise lol.
He needs Sharingan for S/T so that's why he's using one Rinnegan and one Sharingan and he is not Madara he's not capable of switching between Shari and Rinne powers just because he got Rinne implanted not Developed like Madara.
The other thing is that How you know he has other Rinnegan?
What do you mean how do I know, Tobi clearly took Nagato and both of his Rinnengan and only implanted one in to himself, you think he just tossed the other one on the side of the road?
I forgot that we saw Nagato with both eyes closed, but it is not 100% proof but still I do also think he took both, but the reason he's hiding and not using it just because he needs S/T !
Either way I just don't simply see Madara poofing away just because Edo Tensei got canceled haha