Well, Elon Musk's Neuralink is claiming they're close at least, but I could also imagine someone coming from the other direction entirely, and making a robot limb that was autonomous and worked with the wearer instead of being directly controlled (but the failure mode would be no fun...)

Sensory input is the other 50% of the game that remains unsolved. If Neuralink's robot works it will be a game changer for artificial eyes, limbs, everything.

Besides that a robot limb can't be autonomous in it's movement as most movements we do are asymmetrical and thus it needs input from the other limb as well.