The latest rumor is that a major attraction will be leaving Kings Island this year.
Normally, my first guest would be Amazon Falls, because no one hardly rides that... but calling it a "major" attraction is being rather generous.
So my second guess would be Vortex, because more people hate getting beat up on that ride than there are people who enjoy it.
My third guess is Adventure Express, because most of the rides' dark elements haven't worked in a very long time and there is barely any upkeep on the elements that do still work (statues beating drums). Also, the company that made those coasters (Adventure and Vortex) has probably gone down hill, if it still exists at all, since the owner passed away, so replacement parts are going to become more difficult to come by (unless it's something that another company can duplicate, like a lift hill chain). But this is all just theory. I have no claim as to what is really going on with Arrow Dynamics or Kings Island.
The second rumor is that Ceder Fair is adding coasters to five of its parks in 2018. So my other theory is that they could take out Vertigo and move it to a smaller park, like Michigan Adventure or something, and replace its spot at Kings Island with a flat ride or with nothing at all. A used coaster is still a new coaster for a park that doesn't already have one like it. I can't imaging Kings Island getting another coaster after just debuting Mystic Timbers this year, but I guess stranger things have happened.