Since they're all on ESPN networks, it's based on what ESPN wants ratings-wise as opposed to what the SEC wants, I would guess.
ESPN does appear to have more flexibility this year than they have in the past. Before, you knew which network each game was going to be on for the whole season in October. It wasn't great, as you sometimes got good matchups on ESPNU at 9 p.m. and not so great ones highlighted on ESPN. (And it just caused them to lean more heavily on Kentucky for every ESPN Super Tuesday game so that they could be sure they had somebody "interesting.")
Now, they're holding off until a week or two beforehand as to whether the games will be on ESPN, ESPN2, ESPNU or the SEC Network. They just announced that the Alabama game on Saturday is going to be on ESPN2 sometime in the last couple days and still haven't announced which network the Vanderbilt game (next Wednesday) will be on. As it doesn't seem to be affecting the start times of the games, this seems like a positive step.
Also, we're getting tons of positive press from the SEC Network and from ESPN when they're actually showing our games, so I don't think we can use the "Alabama and Kentucky are the only teams they care about" line. Not this year, anyway. Sure, the standard issue ESPN talking heads who aren't specifically focused on college basketball haven't given much thought to anybody but Duke, but so it goes.