Here's how I would like it to go. Madara fights Naruto and Bee and manages to take Hachibi, and when all looks hopeless, Sasuke arrives and saves Naruto from Madara with his new doujutsu, the Rinnegan. The two agree to join forces against their common enemy, Madara, and begin working together against Madara. The battle (I would hope) is epic and intense, with Madara actually going seriously against the two when he realizes that he's, essentially, going against the sage of the 6 paths since Naruto inherited the sage's body and Sasuke inherited the sage's eyes. Madara unleashes Perfect Susano'o and begins fighting seriously, but Naruto and Sasuke still manage to overcome Madara and eventually defeat him. That's when the shinobi alliance reaches Naruto. Naruto explains the situation to them and Naruto is declared Hokage of Konoha by the surprisingly alive Tsunade.
Sasuke looks to Naruto and tells him he still wishes to fight Naruto and the two have an intense fight with dialogue. Before they exchange their final attacks, Sasuke puts Naruto in a genjutsu and explains to him he wishes to follow his brother's path. The two of them then exchange their final attacks, but moments before their death while they're looking into each other's heart, Naruto informs Sasuke of his decision: following his father's footsteps. Both are within the radius of the explosion and both end up dying.
