Katherine Heigl, who played Izzie, recently decided to leave the show, but Rhimes explained that she will not attempt to give Alex (Justin Chambers) closure.
"It's going to linger," she told Entertainment Weekly.
"And I actually feel good about it lingering because [it means] Alex is left with unfinished business. And that's going to be very interesting for his character."
Rhimes added that Callie (Sara Ramirez) and Arizona (Jessica Capshaw) will continue to fight about having babies.
"They're breaking my heart right now with their, 'I want to have a baby, I don't want to have a baby' war," she said. "Because I've actually known people who go through this and it's never pretty. But I like them together and I want to see them together."
Rhimes also dropped hints about the upcoming season finale, saying: "The events of the finale itself change the game. Whether anyone lives or anyone dies is not really necessarily the point of it."
Grey's Anatomy continues Thursdays at 9pm on ABC.