Are their any seniors left in College Basketball?

What happened to the old days of college basketball when all players stayed for four years and then went to the NBA?  Why the sudden change especially in recent years and most likely this year as well.  Kevin Durant, Carmelo Anthoney, Luold Deng, Greg Oden, Josh McRoberts are all victims of leaving early for the NBA.  Yes i am aware that all of these players had extreme talent and would not have been challenged very much in the NCAA however it would have made the competetion and the over all games a lot better. I know the money for the NBA is appealing to all players in College Basketball but i think there should be a rule to make players stay at least until their junior year and then decide if they would like to stay for their senior year or leave early for the NBA. In my opinion this would make College Basketball a much better game and it would be even more intense then it already is.  Players that do stay for all of their years in college usually do see rewards. Some examples ... (link)