I think that it is much more likely they will switch to a non US Airways branded card to maintain the customer relationship with barclays. (and their associated income.)

besides that, there will be some period of announcement on the board as to what will happen with the card. Id rather just cancel it at that point vs pre canceling it. I too will be canceling my card prior to the turn of the year, but Id like to make a couple charges on it at the end of that year in order to have the account activity carry my US Airways points all the way to the elite merger.