Here is the thing. In the Japanese culture, your hair style, just like your name is a big deal on what you are as a person. Your identity. It is a theme followed in both Naruto and Bleach where the characters make a big deal about their name. Just like having blond hair makes you a rebel in the Japanese culture.
Tobi would have no need to hide his face from Naruto now that Madara was revealed to the world. It cannot be Madara hiding his identity further. Now if we look at the timeline, Madara probably died of old age, somewhere between Minato´s childhood, and the present. Even if Madara died during the tme Minato was young, he would have already been an old man, unlike the summon Kabuto did. This means Kabuto brought Madara past his prime by giving him access to Harishima´s cells, and his Rinnegan in a YOUNG FORM. Tobi seems to be doing his own thing, and tried to replace Madara. Basicaly he betrayed him.