Too difficult to prove intent to harm for second degree murder. Manslaughter would also be impossible, the sheriff's office already said there was no intent to harm and its an accident.
However looking at the video there are some very disconcerting things occurring. It looks like he purposely "big leagued" the kid for lack of a better term. Forced him to the outside and made him crash. This is normal but Tony stewart was the only one going fast after the caution flag was put up. Suggesting maybe he wanted to see his handiwork. The kid shouldn't have been out of his car.. but personally I think that an already roadraged stewart was incensed by this and it sounds like he gunned the engine to scare the kid or kick mud on him.. car fishtailed, since he was going 100+, instant death.
Maybe he'll pay a big civil suit for wrongful death but there's no way he'll face criminal charges