Depending on the timing I think James Louis Sobieski may be put forward again. Leopold probably still won't like the idea but turning John Sobieski down, again, and then marrying Maria Antonia to a Neuburg would be pretty insulting. Especially since it was another Neuburg, Charles Philip, who stole away James Louis' other potential bride, Ludwika Karolina Radziwill. So the diplomacy surrounding her remarriage would get tricky.
Also another marriage will probably renew the issue of her rights to Spain. She renounced them on the eve of her first marriage, though that wasn't generally accepted in Spain. So that issue will probably come up again as they negotiate a new marriage contract.