You still have his "team" members. And even if Sasuke and all his team members were to die, the people who want to avenge Naruto, would find other targets for their revenge. Just like Sasuke did. First he only wanted to kill Itachi, that wasn't enough, he then wanted to kill the Leafs elders, (he got Danzo) but it still wasn't enough, now he plans to kill everyone associated with the Leaf.
The strange thing about revenge is, that you will eventually lose sight of your original purpose/goal. It becomes like a drug, once your revenge is fulfilled, you'll grow hungry and then start searching for other targets, (no matter how small the connection is to the original goal/purpose/target).
Example: Sasuke and Naruto die in a fight. People could see that as "Sasuke murdering Naruto." People want to take revenge for Naruto, only to find that everyone who cares about Sasuke is dead. Does this feeling of revenge/hatred/sadness disappear? No it doesn't. It festers, and grows until it co no longer contained. Sooner or later, they will start searching for links between Sasuke and anyone (no matter how small the connection is) just so they can carry out their revenge.
Hope this makes some sense... haha.
The Edo you see now, is Madara in his prime. So, the Edo you see fighting is actually fairly young.
