Like all tech we just need time to make it better and safer, killer robots will be just like this, we need to build fail-safes in order to protect ourselves from them.

Russia, china and the us will never allow the bans on the killer robots because they know any of them could build them in secrecy, while in nuclear bombs you can trace the radioactivity of the bomb with killer bots you wouldn't be able to, which makes them that much dangerous!

We will probably see countries arming themselves up with killer robots until there is a state of mutually assured destruction, and, with time, countries will start to decrease the number of killer robots until there are only a few... Think of the killers robot like the next nuclear weapons, at first there were many, now the amount have decreased!