(if you mean US flagged carrier):
IMHO, the only USA carrier (other then a charter company) who would order now would be DL... as both CO and AA are very Boeing (and MD) centric. UA has said they are not looking at the 380 (in the recent comments about their RFP), and US is committed to the 330 and 350 (although I am sure some of those orders/deposits could be converted to 380's).