My predicting the Browns turning the corner and becoming a legit contender is kind of like my predictions of big E3s from Nintendo. It makes more and more sense as an argument with every passing year, you think it has to be coming at some point, but year in and year out I come away disappointed.
Really, this year's team will go as far as Brandon Weeden can take them. He's got a good group of talent around him on offense and what looks like a scary good defense. Last year he couldn't seem to do anything right; this year, while it's still just preseason, he's shown massive improvements in decision making and downfield accuracy. This year's outcome for the Browns hinges almost entirely on whether he can make the next step and become a solid NFL QB.
If he plays as well as he has so far (again, yes, it's preseason, but he's still been playing against first team defenses) consistently in the regular season, they're a playoff team. If he stays where he was last year, then hey, we'll be in great position to grab Teddy Bridgewater to replace him.