For Heart, this transition was compounded by the changing personnel in the band. While the Wilson sisters (Ann - vocals and Nancy - guitar) remained the constants, guitarist (and Nancy's longtime boyfriend) Roger Fisher left Heart in 1979.
Undeterred, Heart soldiered on, releasing the Bébé le Strange LP in 1980. This is a fascinating album, as the band's music is all over the place - to my ear, this sounds like a group working to rediscover what their sound is. In the midst of this experiment is a great straight-up rock song, "Even It Up," with a cool early video to boot. Particularly noteworthy are sailor Nancy (who seems to really like her Stratocasters), and the sax trio.
Bébé le Strange went gold and peaked at #5, while "Even It Up" reached #33. Heart's greatest hits album was released later in 1980, and marked the end of their first period of mainstream success. I suspect that most listeners and critics at the time would have viewed this as the likely end of the band. Improbably, Heart re-positioned themselves as a pop/hair band in the mid to late 1980's, ushering in a period of commercial success that was even greater than their 1970's heyday.
Heart has remained active for many years, but appears to be on hiatus as of this writing.