Is it universally accepted (or proven via physics) that it will never be possible to survive rabies after symptoms have manifested? Or is it possible that humanity will make it survivable?

Obviously, this topic deals with future possibilities only - it's universally fatal now, and **if you fear being exposed to rabies, by all means, get post-exposure prophylaxis immediately.** I'm speaking of after the virus has invaded the brain. Is this a Michio Kaku Class III impossibility like perpetual motion machines, due to something related to the physics of neurons, or is it possible that the gap could be bridged? Many things that were once considered impossible, such as going to the moon, were later performed and I'm curious about where on the scale a treatment for rabies falls.