I can see Ukraine and maybe Kazakhstan keeping their nukes, but not Belarus since it has no need for them, seeing that they became Russia's ally. If Ukraine kept its nukes it might either become a semi-pariah state with lost of pressure to get rid of the nukes or a wedge in between Russia and NATO/EU, in other words, a country that people actually pay attention to.
Kazakhstan could've had a messed-up, Turkmenbashi-esque dictator that decided to keep nukes and this state would've had more pressure on it than Ukraine I think.