The Treaty actually was intended to air before A New Dawn, carrying the storyline of the final connecting episodes. Production of The Treaty was completed ahead of schedule so the episode aired much earlier than continuity of plot allowed. The Treaty should be considered part of the series' final storyline the first episode before A New Dawn, The Death of Arthur, The Gathering Storm, The Hinge of Fate. This bodes true for the traditional five episode connections the series always used throughout it's run.
Spoilers for this Ep! Story 93 of the comic strip shows that Sir Gawain's loyalties are torn between his half-brother Mordred and his beloved King Arthur. Thankfully, there is never any question whose side our Gawain is on.
Spoilers for this Ep! The Legend of Prince Valiant comics also depicts Sir Mordred taking credit for averting a war when his true intentions are to seize Arthur's throne (Story 100).