I'd hazard a guess that Madara will be beaten by Naruto and Sasuke working in tandem with Itachi's secret powers given to them.
Still, I see no happy ending for Sasuke with Sakura at this point, though I do see Naruto ending up with Hinata eventually, the latest chapters seem to show he's kinda getting over his obsession of Sakura now.
I would think that based on how Kishi uses Sasuke, that in the fight against Madara he'll do a heroic/redeeming sacrifice for Naruto to land the winning blow. At least it'll save Sakura the heart-ache of killing evil Sasuke herself if she witnesses him redeeming himself to take out Madara.
I dunno, these are just random thoughts really...