I'm not buying the Citrus Swirl removal rumor. Considering how popular an iconic it is, not to mention the outcry when they changed the formula, it would be an odd move to nix it from the park. I mean, I doubt it is that expensive to make and I'm sure it makes up for it.
On my last trip, the Citrus Swirl machine was broken and, based on the response, almost every customer in the three lines that were waiting was looking for that one item alone.
My guess is that the move is based on theming and crowd control.