I believe that when Madara spoke of gaining some of Hashi's powers in their last fight, he spoke of the fight we just saw. I think due to this new power, his body heals enough for him to get away and given that Hashi was not aware that he survived, I can only assume that Madara remained hidden until Hashi's death. The current version of Madara (edo zombie) is an augmented version which is Kabuto's doing. You can see this when after Muu summoned him, Madara peeked under his armor and asked Kabuto whether he was the one responsible for what was done to his body.
As for Sasuke, I don't think that he will seek to destroy Konoha. Even though Kishi has kept this hidden so far, I feel that Itachi has made a huge impression on him and i don't believe he wants to destroy what his brother died preserving. I do believe, however, that he will fight Naruto. Not for the reasons we think but to try and get some understanding as to how Naruto has gained Itachi's respect and acknowledgement. Also out of rivalry, to test his strength against the failure who he always looked down on but has somehow gained more respect than he ever has. Whatever the case, the Uchiha's cycle of hatred and murderous streak has to come to an end and unless they are to be completely wiped out which is very unlikely, it will end with Sasuke accepting his brother's way of thinking.