The Talk-Jutsu of Madara Uchiha
So let's start with basics. Madara saved Obito's life so he could have an impressionable young Uchiha to carry out his bidding once he died. He looked very old and near death. Madara implied they were in an area between life and death. I'd suspect this is the same area where Kakashi met his father. Madara awoke his Rinnegan "shortly before his death", in other words AFTER rescuing Obito.
I suspect Madara had Rin killed and brainwashed Obito to carry on his name and legacy, telling him "you are nobody now" after injecting Zetsu/1st Hokage cells into him. This infusion made him on par with Minato and allowed him to easily awaken the Mangekyou after witnessing his only friend (Madara) die. Possibly some of Madara's own DNA got thrown into Obito to allow him to heal up. Alternatively, Obito watched Rin die. So what happened to Madara's eyes? Easy, he gave them to Nagato. That way the Rinnegan powers would survive Madara's death. Tobi told Kanon many a chapter ago that he was the one to tell Nagato to found Akatsuki, to give him Rinnegan and so forth. Nagato was likely not born with the Rinnegan, but Jiraiya had absolutely no way of knowing that.
So we can safely assume that Madara's talk jutsu is >> Naruto's talk jutsu. If Obito does have a change of heart it will deeply cheapen his character at this point. But since Nagato got done in by some cheesy Naruto promises and a mere book, I'm guessing Obito will fall after Kakashi or someone else's goes out on a limb for him.
Madara's true goal is NOT the "Project", it's likely just some BS he cooked up to string Nagato and Obito along. I'd say his real goal is to become the 10-tails jinchuuriki. We've seen from his first appearance that he's a douche that just wants power. He wants to become the next 6 paths and regards this as his right for awakening the Rinnegan. He was too old to enact this plan at the time of his death, so he needed to have other's do it for him and to bring him back to life. My guess is Madara wants the 10-tails power to become an actual living, immortal God.