I would stay. They need to expand their performance abilities, develop their skating skills, and gain experience. That happens over time. Usually it happens by skating to programs that aren't tailored to your strengths but force you to develop new strengths. In hindsight, going back to the old FD probably wasn't the right choice. But the nerves would have been there regardless, and if S&F had struggled from those nerves with the new FD, people would have second-guessed & said that they should have used last season's program. S&F wouldn't have defeated this particular set of performances by Fournier-Beaudry & Sorenson anyway.
Ultimately, this was your classic sophomore slump type season (though technically it is S&F's third senior season together). They outperformed expectations last year so this year there were expectations, and that very often takes time and experience to adjust to. Anyway, it's part of the process. Hawayek & Baker, Zagorski & Guerreiro, Popova & Mozgov all experienced or are experiencing the same thing. Teams usually go through this either the year after they leave juniors/win Junior Worlds. Or--if they come on gangbusters that first season--the season after it. I find that the best thing for teams to do in this scenario is 1. stay together and 2. take advantage of the off season and get to work. On the positive side for Soucisse & Firus, they really looked like they dealt with the disappointment well. Had real perspective in their reaction. I think that's usually a good sign.