According to the report, "The bitter feud between Chase and Harmon was a major factor in destabilizing the show for a couple of seasons, leading to public outbursts and profane voice messages. Now that Chase is gone, emotions have cooled down and all sides involved have had time to reflect, there is speculation that Harmon may come back, especially if this turns out to be Community‘s final chapter. (I’d heard that, with the show’s future at NBC in limbo, there were a number of suitors clamoring to pick up Community for a final installment.)"
New showrunners David Guarascio and Moses Port, with a history on safer, less-experimental shows like Just Shoot Me and Happy Endings, failed to bring up ratings during season four and, by and large, received warm reviews but nothing like what Harmon had been getting. A return for Harmon would likely be a boon for ratings, at least in the first few episodes back, and would certainly engender a lot of goodwill with fans who have been complaining about the Harmon-less Community all year long.
Harmon's pilot Rick and Morty was just picked up for a full season on Adult Swim.