while we never did get to see madara with his third eye, just going off how that fight had been going, it wouldn't have mattered much. if they would have continued to fight madara, they would have already won. it's doubtful he would have been able to move through dimensions, well i don't really know, but he would have known no jutsu for that eye. but even still, he wasn't really a challenge for naruto and sasuke, which is why kishi had kaguya come in to fight. by all accounts, she actually is a challenge. had she really had any real fighting skill, this would be an even worse fight for them. luckily they have the fighting experience in this.