No, I think it's a clone, as another person pointed out on another thread of mine.
If you look closely, you see the cracks on Madara's face in chapter 600, but we know that when he released himself from Edo Tensei those cracks were supposed to have disappeared.
Now I'm just guessing that what happened is that Madara made 26 clones instead of 25 back during the fight with the Kage, and sent one clone ahead to check out the "fun" Obito was having. This would explain why that Madara still has cracks on his face. The original is still facing the Kage.
That's just a hypothesis, though. Can't say for sure.