The debate about Obito being a credible Tobi aside, it seems to me that now Madara has appeared there could be a potential cause of conflict between him and Obito. Madara is after power and domination and is seeking the Kyuubi for this purpose, yet he turns up and finds Kurama is inside Naruto so can't be summoned. Then he see's Obito has been busy and has almost managed to resurrect the Jyuubi; it would be natural for him now to attempt to control this new beast.

The fact that Obito was rushing to complete the Jyuubi suggests that he may have feared Madara would appear and attempt to take the tailed beasts for himself.

Also, if a fight breaks out between Madara and Naruto there is no guarantee that Naruto could use Kurama's chakra or tailed beast mode at any rate in battle. Sasuke managed to enter Naruto's conscience to dispel Kurama and Madara should be extension also be able to do the same. The only thing different I see this time around is that Naruto has a portion of Kurama's chakra for himself so that may not be so easily dispelled, if at all. Tailed beast mode however is something different. For all we know Madara may even try and take control of Hachibi as Bee is in tailed beast mode right now. Bottom line for this being, we may see Naruto having to resort to Sage mode to for this fight and use strategy more than just brute strength with Kurama's chakra.

How would Obito react to this? Well it is a really long shot but he could team up with the Konoha crew to fight Madara, having a change of heart midway through about why he has been bitter all this time and then really die by trying to save Kakashi/Naruto once more. Who knows, he might gift his last Sharingan to Naruto who may become the most powerful Uchiha/Senju (Uzumaki) combination produced so far. He certainly wouldn't have any chakra or endurance problems in maintaining the Sharingan.