Assuming that she is still single or that the dauphin is still widowed on schedule. If Maria Teresa lasts until, say, 1750, no way they haven't found an alternative candidate for Maria Antonia by then. Admittedly, there is a shortage of candidates, but matches to Savoy, or her OTL one to Saxony, for instance, are still possible. George II was looking - in the beginning of the 1740s for a Catholic bride for the duke of Cumberland (either an Este or a Savoyard princess) as a way of separating Britain and Hannover by violating the Act of Union. Unfortunately, the '45 intervened, and no Catholic girl wanted to marry "the butcher".
Uprising was in August 1745, (after Pfaffenhofen in April), so things might go differently (as in the rising flames out like the 1715 or 1719) and Maria Antonia could end up married to Cumberland (a match with the Netherlands makes more sense than a match with Modena or Savoy) or in the event of a victory, to Bonnie Prince Charlie.