The merger between Comcast and Time Warner Cable is no longer as certain to get approval as it once was, and the two cable giants know it. Wall Street Journal sources understand that the companies will meet with Department of Justice officials this week (the first time they've met since the announcement) in hopes of negotiating concessions and saving the deal. It's not clear what more they'll propose beyond existing offers, although history suggests that they could give up more customers or promise more efforts to expand low-cost internet access.