AA/US is going to have a very diverse fleet not much different from DL as a result of two very different fleet philosophies before the merger and a lot of orders from both manufacturers on the books on the day of the merger.
It is doubtful that Airbus will accept cancellations of 330s w/o significant increases in A320 family orders.... possible but I don't think the 330s are going anywhere.
It still might make sense at some point in the US industry for the big 3 to start swapping planes to improve fleet commonality but I'm not sure that has been proposed yet.