I think Isabeau's in trouble in that she's no longer the clear number one. Amber, if she could put together two clean or nearly clean programs, is certainly in the conversation. Alysa, if she gets back into her prior form, is certainly a contender - especially now that her PCS is improved. Bradie is still trying to come back. Lots of the younger Seniors and rising Juniors (Ava, Lindsay, Elyce, Sarah) have made quite a splash last season/this season. There's lots of US women that could beat her now.
The other trouble I see it that Isabeau has said she knows she needs to fix her jumps, but it seems there's no effort to change them: no coaching change, no improvement in technique, etc. The jumps haven't failed her yet, but I think every skating fan knows that the failure is coming - how soon is the question. We saw issues last year, and at Nebelhorn we're seeing the judges really start to hammer them.