I can guarantee that if Comcast decided to dump NBC during their next negotiation NBC would be willing to do any deal Comcast wanted a couple weeks later.
Your example actually disproves your point. NBC is owned by NBCUniversal, which is owned by Comcast Corporation, which happens to be the elephant in the room for both U.S. TV and broadband service. Until last week, Comcast thought it had a snowball's chance in hell of buying up even more market share (Time Warner Cable) and put even more of the cable companies in the same bed as the content companies. Clearly the business model is working for Comcast -- no reason to think it won't stop any of the publicly-traded cable companies (e.g. Charter, Cablevision) from merging with one of the publicly-traded content companies (e.g. AMC Networks, Starz, Fox).
If Verizon can afford to drop The Weather Channel (a NBCUniversal property) from FiOS TV without warning, without lowering the monthly price for subscribers, replacing it with an inferior product (Accuweather, and I can't figure out which is more useless, their TV channel or their inaccurate forecasts), and with barely a fight from Comcast, that's a win for consumers, right? Bueller?