Why? He is of an age and net worth that if anything he needs diversification. Dan Duncan's family (founder of EPD) had all sorts of complicated estate issues and plans because of MLP structure. It turned out that Mr. Duncan had the "good fortune" (if you are going to die anyway) to die in 2010 and he along with George Steinbrenner and a few other mega-rich paid ZERO federal estate taxes.
I don't think Kinder would buy out KMP because he already has too much of his wealth tied up in the KMP family.