Eh, no North Korea won't do it, well at least if they have any brains left in their military.
Though, either if they really are that desperate(or stupid) or the Chubby Son of Kim Jong Il thinks War is a game, then they might do it. In the long run however North Korea would lose.
Russia won't commit anything in terms of actual troops or fighting, arms sure, the military tech between the two countries is compatible so its not hard for a North Korean soldier to drive a Russian made tank.
China risks the whole world's condemnation if it so much as sniffs North Korea's ass, this whole "New China" thing would all go down the drain should they back NK. As has also been stated above about their Economy and such.