Ask yourself this simple question: what is Sasuke going to do?
If he joins this fight right away, Kishi will have started up the "time to learn the truth, conveniently exit stage left from the battlefield" thing for absolutely fucking nothing.
If he learns "the truth" before joining the fight, it would require dragging the "final battle" out a lot and then Sasuke would either completely ignore "the truth" and have wasted all that bullshit or he'd be care-bear-stared without ever having had his 'final battle' with Naruto.
If he does not do jack fuck until after this fight, why will we give a shit
? I mean honestly, anything that happens after the current fight with Naruto is basically inconsequential to the plot. The grand finale "Naruto v Sasuke" will be a gigantic "who the fuck cares" moment.
I mean, really. Did you actually think I was saying "THE MANGA'S GOING TO END WITHOUT SASUKE GUIZ"? Are you that fucking desperate to find something to rag on for a random guy on the internet