I don't see 2k wanting to jump into College Football. They dropped out after 2k3. If they really wanted to make a college football game, they would have after they lost the NFL license. The demand for a college Football game is higher now then it was. So whoever develops a college football game, should see good sale numbers. You'll get hardcore gamers who want another football game, collegiate athletes who want to play as themselves, and college football fans. NBA is 2k bread and butter. But can afford to devote resources elsewhere since game is solid enough. But I feel they are holding out for the NFL. I don't think they want to develop a new football game unless they feel it will be profitable and have sustained success. I don't think it would be as easy as using APF gameplay engine. So if they have to build a new football engine, they will most likely wait for NFL.
If 2k makes a college game, I think it would be CBB.