Today, CBS launched a new standalone streaming service that includes live streaming in some markets. Yesterday, HBO announced their intention to offer some type of streaming product in 2015. As I've written before, the major cable companies have no incentive to break apart the bundle. So why are HBO and CBS apparently doing so? First of all, I'm highly skeptical that HBO will offer the full HBO GO product without a cable subscription. My hunch is that new content will be delayed, or it may not include any movies, or it will be very expensive ($20+ per month).
As far as CBS goes, they probably have less invested in the cable bundle than any other major TV network. The only other major channels they own are CW and Showtime, with some other smaller ones such as CBS Sports, FLIX, TMC, and the TV Guide Channel. Showtime produces some nice premium content, and CW targets younger viewers with shows such as The Flash and Vampire Diaries. Perhaps they have similar plans to launch streaming services for those networks or to make that content available without cable in other ways (similar to the deal they did with Amazon Prime to make episodes of Under the Dome available shortly after they aired). College sports from non-major conferences makes up the majority of the programming on CBS Sports, and they already have a college sports streaming service.
CBS doesn't have much to lose by breaking apart the bundle, certainly much less than the other big networks. It makes sense for them to make their content available in all sorts of ways. I doubt any of the other major networks will follow suit, but perhaps some of the smaller independent networks will (AMC, Discovery, etc).