The 0.0000001% chance that Obito defeats Madara and reveals they were all in infinite tsukiyomi all along came true. The Shinju's eye was already open, so it's possible, just insanely unlikely.
I think Obito taking out Madara in the end is highly plausible, tbh. I can see him doing a Vegeta/Buu sacrifice type thing, which would in turn redeem himself in the eyes of the Alliance.
If it turns out they were in IT, I'd be in total disbelief.