A lot goes into determining when a ride closes -- ridership, downtime, marketability, maintenance costs, possible renovation costs, staffing costs, real estate development opportunities, etc. It reached the end of it's service life for KI, but that doesn't mean someone else can't buy it, renovate it, and operate it.
My guess is that a possible buyer would only be buying the track, supports, and trains. I assume that due to its age the control and logic systems are extremely outdated. I'm sure KI has made countless modifications over the years that probably just wouldn't work once disassembled. If a park picks it up for $8-$11 million, and they invest another couple million into completely redoing the electrical systems, they'd essentially have a brand new attraction on their hands for less than $15 million.