Mike Cavanagh’s bombshell announcement on Thursday morning seemed almost like an afterthought. There he was, the former JPMorgan Chase investment banker and C.F.O. turned senior Comcast executive—and the interim C.E.O. of NBCU since Jeff Shell exited the business—babbling on about “convergence” and Epic Universe, the company’s forthcoming $150 million Orlando theme park, when he nonchalantly dropped the news that Comcast was studying the idea of sending out to sea its increasingly forlorn set of cable TV channels. “We are now exploring,” he said, “whether creating a new well-capitalized company, owned by our shareholders and composed of our strong portfolio of cable networks, would position them to take advantage of opportunities in the changing media landscape and create value for our shareholders.”