If Kurotsune's words are correct (And truthful), the story's been done since Episode 3. So, chances are, Ame is not going to change anything regarding the story, apart from a few tweaks here and there.
But instead of thinking about what Ame should do, think about what happened already: It is true that we haven't seen Serra a lot, but when you consider that the last 2-3 episodes we've been stuck in the circus with no real way to come back (Apart from using Surf and reaching the cave near Shade's gym), it is only expected that we wouldn't have seen Serra.
When you consider that the character is not supposed to have any contact with the city/Route 1/*Other places go here* since episode 11-12 (Don't remember), then the lack of "action" from Serra makes complete sense. Serra might have done a lot of stuff that we don't know about because the character is "isolated".
(Although, to be fair, i'd expect some News about Serra if she was actually doing anything. She might not be a famous model anymore, but she's still a gym leader. But then G.Gardevoir left her to look for Luna... i'll just stop right here).
And last: Ame mentioned that some old faces are going to reappear in episode 15. I wouldn't bet on Serra, but there's a small chance she'll be there. I don't know what she would be doing though.