Sasuke's matched or exceeded every ability Itachi had. He's gonna pull out that sword and shield too, no reason to think Itachi didn't pass those on with his other powers. I'm liking his new development, he's always been the angsty one but usually went nonlethal. He seems to be cutting people down in earnest now. I guess it's unlikely he'll mow down some named characters since they just got properly introduced, but hey why not--he's gonna be on trial for war crimes anyway for attacking the summit, why fuck around now? At any rate he's gonna tax the hell out of his eyes in the upcoming fights, and Madara will probably offer him Itachi's eyes before he sics him on Naruto for their final round.
The byakugan thing threw me off too, we were told sharingan was the evolution of byakugan but that's obviously backwards if the two original lines were Sharingan and Mokuton users.
If Naruto is a Senju descendant, we'll need more backstory on his parents to explain the link, and that's a win-win whichever side he gets it from.