I know Kat is careful about what she brings here......SOD, & Jason 47 are most reliable.
SPECULATION
I was thinking that some character were let go, written out, scripts filmed, etc. And then, they had major characters or rather the actors portraying them, leaving of their own choice. Tired of whatever was going on behind the scenes, whether in the writing room, producers' room, or whatever. suddenly it wasn't just Will, Sonny, Rafe, Gabi, but also Hope, Ciara & Eric all saying adios.
I keep imagining the scrambling going on, the juggling, the arguing. They had already fired their long time and best producer, Greg Meng..........and thus Rafe & Gabi will be returning (wonder if that nasty bunch of thugs after them changed their minds???, lol). And they talked Ali Sweeney (Sami) into returning for a longer stint as well. Plus talked Marci Miller into reprising her recasting as Abby.
The other new faces n the Fall Preview had already filmed their appearances before the shutdown in March occurred.