As someone said I think without Harmon it could improve, showrunners/creators aren't always the best person to take it forwards. How much is Harmon, how much is Sony, very hard to tell but the show got worse. Is it because it had the same budget, better paid actors so they did far fewer big scenes, walking around campus, multiple stories in multiple locations? Maybe, did Sony hack the budget back, or did Harmon pocket the money, or simply did Harmon do what so many writers do, try to push the boat, and fail miserably.
As for being creative..... he was and he utterly wasn't, ultimately he ripped the story line of the entire first and most of the second series by simply copying cult films. It's both original.... and very easy, it meant half the writing was done for him, translating the idea's to the campus was easy. The idea for Community was great, the writing in the first season was great, but creators don't always make the best showrunners.
He's mostly changed the characters to be very one dimensional, the locations/style of episodes has changed almost completely and its just not as good.
A new runner with the mandate to make season 4 like season 1 with some fresh writers could be epic, a new runner with the mandate to make a chip as possible short series with as few extra characters as possible could be completely awful.
For anyone that hasn't watched Happy Endings though, its a really freaking good show, like really good. I'd rate both series of it above series 3 of Community.
It can end up as anything, but I won't judge it till well, I watch it. Hoping for the best though, very good cast(though it could happily lose Shirley), deserves a great last series(if it ends up being the last).
I've read multiple things about Harmon being difficult and frankly the whole Chevy incident just screams he's that kind of person. Anyone could see he was purposefully writing Chevy as a more and more ridiculous character to embarrass Chevy, ultimately thats why I think him going could be the right move, when you harm the show to pee off a character who had previously been brilliant.... you're doing something very very wrong. If you didn't want him on the show to start with, too late, boo hoo, get over it, he was great casting by the network and a great character, ruining that because you get a bit big headed and want to force him off the show, rather than utilising a character who was great is utterly ridiculous.