There's no deterring the fans, but for the rest of humanity, I'd have to recommend against the film. The biggest problem with the whole series is Lambert, who just can't hide his French accent with a Scottish one. The rest of the cast is of little help as they limp and bound through the ridiculous screenplay. This allows the film to be almost lyrical at times, even if it doesn't attempt to make sense. As long as it keeps moving from swordfight to swordfight, and flashes back to Old Scotland periodically, the fans will be happy.
Endgame delivers that basic formula, but never attempts to go beyond it.
Just don't bother me with any more sequels.