Naruto's arm is bandaged to hide the hashi cells/zetsu arm we don't know if sasuke got one yet but in the sketches for the last he's armless maybe he would get it in the movie or after
I don't think it's been made clear yet. I thought that Naruto had a metal prosthetic in Chapter 700 because it looked kind of greyish, aha. I don't think I'll be watching the last though, it looks like a complete trainwreck.
Its hard to predict, It seems like he refused to take the arm because he felt guilty and thought he deserved it.
I do think he would accept it eventually after he comes back to the village.
I'm guessing Naruto uses the bandages to cover the Zetsu arm since it looks different.
He didn't "refuse" the arm. He left before it was completed. In the last he has no arm, because he is just barely getting back to the village. It is very possible that he was an arm in chapter 700.
Sasuke probably doesn't have one, he denied the operation. Although his "hashirama cells that Kabuto put into him" should have healed his missing arm, that is if he had them U_U
As for Naruto, I don't know why his arm is still bandaged up like that, must be for cosmetic purposes, like Lee for instance but I don't know.