Well I think you have to talk about what they are. I mean they've won 5 straight and they are still only at .424 win% which is a 69 win pace over 162 games. So, what exactly are we talking about in terms of maintaining this level of "success?" .450 win%? .500? The problem I have is I think everyone would say the cubs would be far exceeding their talent if they played .500 ball. However, at the moment .500 ball doesn't even get you into the playoffs. St. Louis is 1 game over .500 and are still a half game back in the wild card. So, if we're talking about a .500 team you're talking about a team that is playing well above what most would consider their talent ceiling and it's still not good enough to get you into the playoffs.
Again, they might not totally break the team up but I can't see them adding high profile pieces to that via deadline trades because they aren't there yet. And in the case of Hammel, he's gone at the end of the year unless you re-sign him. He's 31 as well so I can't see them wanting to re-sign him. So, I think he's gone regardless especially when you consider he can net a real prospect.
Other than Hammel, what's there to break up? They aren't trading Wood, Rizzo and Castro. They probably can't trade Jackson. There's no reason to trade Arreita. The only moveable pieces are Shark and some of the lessor guys like Bonifacio, Russell, Villanueva and Schierholtz. And as I said before, if they play exceedingly well, maybe they consider keeping Shark. But, the rest isn't really that much of a loss.