i highly doubt that Kings Island will switch over to Pepsi. im not familiar with any contractual agreements with Coke but i would imagine they exist. i do know, however, that one of the main reasons why Coke will remain in the park is because all of the lines that transport the syrup are technically owned and were put in by Coke. if the park switched to Pepsi, it would be a pain in the ass to remove all the lines and put Pepsi's in and it would cost too much.
p.s. im sick of people on this site posting who don't know what they are talking about. pretty much if you don't work in the park, you don't know anything about what/why anything is happening.