I don't know if all conferences are. I think the ACC and Pac-12 are but not sure about Big-12, B1G, or SEC. If they are then I wouldn't be surprised to see the Big East do the same. However, that would put a cramp into the whole notion that two divisions saves on travel costs because now you're looking at 4 non-divisional games. So 5 in division and 4 games in the Western Division?
The Big XII will have a 9-game conference schedule as long as membership is 10 teams. But, if they go to 12 or 14, they'll consider an 8-game slate. That is part of the appeal to some of the ACC teams they're targeting, who are ticked about having to give up an OOC game as part of the their 9-game slate that will start in 2013 (assuming Pitt & Syracuse join for that season).
The Big Ten and SEC are sticking with 8-game conference schedules, b/c it allows for 7 home games annually and protects some of the more valued OOC games their members play: Florida/Florida State, USC/Clemson, UGA/GA Tech, UK/Louisville, Michigan/Notre Dame, etc. With a 9-game conference schedule, you have to give up one annual OOC home & home game in order to maintain 7 home games annually. Otherwise, you end up with 7 home games one year and 6 the next, which is a big kick to the wallet of these schools.