Well, it ended too soon, BUT I found out PBS left off a text ending which apparently said something like the following:

Note: In an airing of the show by Knowledge Network in British Columbia, a text title appeared at the end of this show, stating that Mrs. Pritchard, feeling that she had served a purpose, resigned as Prime Minister, and she and her husband are living happily at home with their family in Eatanswill, with Catherine Walker becoming Prime Minister and is successfully leading the Purple Alliance, noting she never married. The title card was not aired by PBS in its airing.

Little more satisfactory of an ending than just leaving it hanging without even the promise of another series to carry on!