In 1977 Frankie did indeed "go solo" but the Seasons as an entity were retained. The idea was to see whether the public could stomach a 4 Seasons without Frankie Valli fronting them. They wouldn't and there were some uncomfortable performances for Gerry Polci, Lee Shapiro, Don Ciccone, and John Paiva until the experiment was halted.
I don't think that Frankie Valli is in this photo. Very weird????? The quote above is from the 4 seasons website.