Normally if you get a copyright on something, it takes at least a few decades before anything happens to it. If a copyright expires, it just goes into the public domain, like Sherlock Holmes. It basically means anyone can do whatever they want with the IP, without needing anyone's permission (Which leads to re-imaginings like the BBC's Sherlock series). However, since Disney decided to muck about with copyright laws in order to hold onto Mickey Mouse indefinitely (Like 70+ years longer), there is a chance for an IP to kinda get stuck in limbo (eventually leading to abandonware).

So the worse case scenario is that someone buys the SK IP, liquidates it (basically sell what can be sold and dismantle the rest), and then does nothing with the IP. You don't need to worry about the copyright expiring.