Not necessarily. Prediction gives you the end result, not the path that gets there. Delphie Predicted that Wanda would not be in her charge for long, but she did not foresee that the way that was achieved was Wanda becoming Chief caster.
Olive will be Wanda's Chief Caster, but that can be achieved in many ways, including Olive being captured by Goodminton, Turning, and becom,ing Goodminton's Chief. Or both Olive and Wanda could be captured by an unknown, yet powerful, third Side. There are a myriad of ways to get tehre, without Wanda being captured or traded and winding up in Haffaton.
I think this text period may be more about demonstrating the flawed vision of the Predictamancers than anything else... except the decent of Wanda, of course.
Why place any faith in Goodminton's Predictatrickster? Even when it comes to her doomsaying, she could be seeing the fall of Faq instead of anything useful to Goodminton. Or just be the prophetic equivalent of a broken clock.
Will she? Really? I see no reason to believe that. Every word said about her fate could easily have been a lie intended to make it happen, she may even be purely fictional, invented as bait for a loathsome trap. If she does exist and really is fated to be Wanda's Chief Caster, maybe Wanda will become an Overlady and a certain flower girl will come looking for a job. Or maybe Olive will bond with an Arkentool, or will turn out to be Charlie. Or perhaps she'll be the most powerful Caster in a three way link Wanda gets hooked up to. Really now, any 'entwining' Wanda and this semi-mythical Caster do may be strictly confined to the Magick Kingdom for all we know.
Wanda's always been froody, 'lying is bad' is the moral here, so far at least.