The arms are made from Hashirama's cells which means that they are perfect arm replacements. Sasuke refuses to have the arm implanted because he wants to explore the world with his own body. His scars are a reminder of when he turned a new leaf, so he will probably never have the arm attached.
Sasuke will not get his arm back, he does not want it back. Sasuke's missing arm is penance for his past crimes, punishment for the many lives he has destroyed and taken while on his path of darkness, and a reminder of why he is now on a mission of atonement.
Sasuke's Left Arm Was Torn off after the final clash with Naruto. The final chidori-rasengan showdown resulted in both of their hands getting ripped off. Tsunade Created Prosthetic arm using Hashirama's cells, For Naruto and Sasuke, which the latter refused.
More precisely, Sasuke Uchiha rejected a chance of getting a prosthetic arm. As he left Konoha to roam the world, he was offered a prosthetic arm, and had to wait around for that, but he chose not to get it.
Unlike Naruto and Sasuke, whose healing is autonomous, Sakura can't heal autonomously unless her Byakuguo Seal is unleashed.
Your eyes (in real life) can heal, but whether you still have vision/can use the eye is another thing. Depending on the direction of the plot, it's possible Sasuke may lose his Rinnegan. Just because things can heal doesn't mean they will continue being the same.
It's entirely possible that Sasuke's eye could recover over time, but if the series is smart then it'll be quite a while before he'd be able to do so. But there's a greater chance that Sasuke has lost his Rinnegan for good.
S6 (when Kenny was dead and replaced with Timmy): Timmy, Timmy, Timmy, Timmy, Timmy, Timmy, livin' a lie TIMMY! S7-S10: Someday I'll be old enough to stick my d--k up Britney's butt! S10 Episode 8-Present: I like f-----g silly b-----s and I know my p---s likes it.
Essentially, if you sent a voice message to someone and they chose to keep it, you'll see a “Kept” indicator beneath the voice message to let you know that the message didn't expire.