I would be very worried if I was the ACC, Big 10 or PAC (they have already been left behind the big boys). Why? Go look at the most watched games over the past few years. They were almost all already in the SEC. Now you are adding two blue bloods of college football with huge national followings. It wouldn't surprise me if the SEC TV contracts were double the Big 10 or ACC contracts.
The Big 10 seemingly needs to do something to respond, but the remains of the Big 12 do nothing and going all the way out to Los Angeles seems like a recipe for failure...although it may be what they end up doing. I do wonder if the Big 10 now regrets adding nothing in Rutgers and very little in Maryland. Those along with some older members dilute the brand of the Big 10. With its new 16 teams the SEC would only have 1 stadium under 60,000 (in Vanderbilt). That is impressive.