Not sure if that's true, at least in the LA Market. I predict FS7 owners will keep getting hired for a long time to come. Unlike a couple of years ago, the FS7 is now firmly entrenched in this market, I don't see those clients and producers suddenly getting hot for a FF version.
Every camera has its cycle. The truly dominant models like C300 and FS7 may have a longer lasting one but, at some point, they all become old news.