You guys are completely overlooking Dek’s argument. He’s not saying simply that it the Last Crusade wasn’t meant to have a sequel, but that the film was explicitly designed to preclude the plausibility of a sequel. While you can say the former about Star Wars, you cannot say the latter. Very different arguments.
Actually, you can definitely say that about Return of the Jedi.
EDIT: Frink beat me to it.
Did I say you couldn’t? (by Star Wars I mean SW77)
I don’t necessarily agree with Dek that this means there can’t ever be another IJ movie, but at least argue with him on the correct terms.