I just can't see Vortex being the ride that is removed. It's really popular with the GP, no matter how much enthusiasts love to hate it. Plus it really fits well with the aesthetic of the Coney Mall area with its classic feel. Removing it would really detract from the atmosphere of that area IMO.
Firehawk, on the other hand, is apparently a maintenance nightmare. It has never really fit in well with the Kings Island coaster line up, and I think a lot of people just kind of forget that it's there since it's sort of out of the way. Plus, it's blocking in what could potentially be a pretty large expansion area.