This feels no different than the time people assumed Pain would be the final villain. Obito is NOW Nagato, he is going to get redeemed into a b****. This is why Obito is secretly interested in what Naruto has to say, meanwhile madara isn't so much as he is way past obito in terms of wisdom. There is still hope in obito, naruto and kakashi just have to hit the sensitive points in his heart and will break eventually. But Madara, hah! He doesn't give 2 sh!ts about peace, he's all about war and world domination. That's the guy you want to take out.
Madara is the founder of tsuki no me project. Madara stole hashirama's power, Madara awakened the rin'negan, Madara unsealed the gedo from the moon, madara created the zetsu to gather information on ninja villages. Madara broke obito's will and manipulated him to do his bidding. Madara will the one to become the 10 tails's jinchuuriki.