"I've looked ahead. This is like those Harry Potter movies. Characters you think are gone, then they come back. I've looked ahead on the script and Alicia, they have her coming back," Shelton said.
"Gwen is coming back. We love Gwen," Keys added before joking, "Hopefully Gwen can replace [Blake]."
Stefani herself confirmed in the interview that she has no future plans with the NBC reality competition.
"I don't have any plans to come back, but I definitely let everybody know I love being here and I'd love to come back," the singer said. "I'll be here to hang out and hang out with Blake."
"Gwen is set on leaving, and it is Blake's choice if he wants to go with her," a source said.
Shelton and Stefani first met on The Voice in 2014, and started dating the next year following their splits from their respective spouses, Miranda Lambert and Gavin Rossdale. The Voice Season 12 will air its finale Tuesday.