From what my cousin told me, he tore several muscles in his last match, and was released (essentially fired, but without the negative connotation) from the WWE because he was too hardcore into these matches and was more or less killing himself no so slowly but still surely.

I remember hearing within the last year or so that Kurt told the media after he won the gold, he was offered a contract by the UFC, but turned it down for the money the WWF was offering. He then said that had he known how popular the UFC would become, he never would have signed with the WWF. So it's likely he COULD go MMA, but his injuries are apparently very severe and he most likely wont be able to heal up and then train in time for a fight any time in 2007.