One thing to consider is the lifetime battery warranty.. Once you let go of the car, you won't find another EV with lifetime battery warranty. So, if the Kona works for your needs and you don't really want any other EV because the Kona can fulfill your vehicular needs, it may be a better option to get the new battery and keep it.. If I wouldn't need Supercharger access, towing ability and more space, I would keep the Kona forever..
I'm really bummed out because the wife didn't want to keep the Kona for herself but instead opted to keep her BMW i3.. just because she likes the looks of the i3 better... 300 mile range vs. 120 mile range on the i3.. and yet, she wants to keep the 120 mile range car.. Oh well...