Mace dieing trying to save a young boy stuck in the crossfire in the war, is GLORIOUS. A jedi is the protector of peace and justice in the universe, and Mace being a Master Jedi is looked upon to be a great leader to show no fear, because there is only the force, as the temple teaches. Now SLJ said he won't go out like a punk, but did he mean the character Mace or as an actor. Because if he meant that Mace won't go out like a punk, then in that fan script he clearly won't out with a bang. Sacraficed himself for a life, a life of a young boy.
Jackson has said that he doesn't want to die by Boba Fett and I imagine that Lucas will respect that wish, as he did with the purple saber. Anyways having a kid kill the 2nd greatest Jedi is just plain dumb. Mace Windu will have to die at the hands of Sidious/Dooku/ or Vader because thats what the character diserves. I don't know why Boba will be in EPIII, maybe just in a meeting with a few other bounty hunters(like ESB) with Palpatine and Vader discussing the Jedi Hunt, but it definetely should NOT be killing Mace.