CEO Ted Britt, battling cancer, says the company is in good hands
The Time Warner Cable executive had planned to retire by year's end before he received the diagnosis
Moonves calls Britt's "so-called proposal" insincere and "egregious"
The retiring Britt will be replaced by Marcus at year's end
Glenn Britt, Time Warner Cable's CEO since 2001, will depart at the end of the year, the Wall Street Journal says