I don't think we can judge the offense's potential fairly until the OL is reliably better. That has to be Emery's FIRST PRIORITY this offseason.
As for the receivers themselves, well it's been a cluster fuck out there. My takes is this.
Marshall: No doubt the best WR talent to ever play in a bears uni in my lifetime. He has had some drops sure but in the broad context of his many targets and great catches made (that never would have been made in years past) his miscues are trivial. He is one of the top 5 in the NFL especially with the connection clearly shares with Jay and the fact that he's really grown up with regard to his former off-field issues. Brilliant move for cheap by Emery.
Jeffery: I love this kid and its too bad he's been injured so much this year. He's going to be a star with a Cutler who is protected. No doubt in my mind. Great pick by Emery and I think time will prove him to the best WR of his draft class. Better than Blackmon, better than Floyd, better than Hill or Wright. He could/should have caught that TD pass on the broken play last weekend, but ill give the rook a pass.
Damn I'll be excited to see what these two can do next year if Emery can upgrade the OL this offseason like he did the flanker position last one.
Bennett: Been disappointed in his production this year but I blame most of it on injury and tice's stupid over-targeting of others rather than Earl. He's a very good #3 man and a very sure handed possession guy. His wide open drop against Seattle sucked, but that's a play he makes 99% ofa the time he isn't concussed and staring right into the sun (I was there and the sun came out bright for 10 ,minutes all day, at the perfect angle to jack up that play). He's a keeper.
After that, the pass receiving talent level drops off like a sheer cliff. Between Davis, Spaeth, Adams, Hester, Weems, and Sanz, there isn't a single plausible "good 4th option". Bad route running, inability to get open, bad hands, too small, lack of speed...it's all there is various combinations with these guys. Since Alshon, Bennett, or both have been out so many individual games this year, you can see the problem. There has been no "next guy up" like Green Bay has in Jones and Cobb and Finley.
Upgrade the OL first, get an OC who also involves Forte and maybe ERod in the passing game, and then if possible find a 4th TE/WR receiving option. I'd be shocked if Cutler and the offense wasn't explosive next year under those circumstances.