The 757's are going to go the highest bidder...they're in demand, particularly with Rolls-Royce engines.
With the 787's getting later and later, Continental's long-range fleet is under increasing pressure. Not enough planes and too many international flights. I'll bet money that the 757-300's end up at Continental for several reasons. First of all, they've taken extra -300's off their hands before and they've openly stated they wished they could have more. Second, acquiring these would mean they'd have more -300's for the dense transcon's, which means more 757-200's could stay on international duty, which keeps their widebodies flying across the pond until the 787's start rolling in. It makes fleet sense for Continental to take these. They've got routes screaming for 757-300's but are being flown with 737-300/800/900 or a spare 757-200 that could be utilized elsewhere.
With US Airways, they've got a long-term deal with Airbus and, regardless of the benefits the -200's would provide for a couple of years, that makes it that much longer that they'd have 757's in the fleet and it's just not a smart decision for their fleet plan. They need to be losing them, not gaining them, no matter how superior the performance is to the A320 series. US is going to drive their 757's into the ground.
I'd say the 757-200's could end up anywhere, but Continental is a possibility. It would be ironic if FedEx ended up with them, given the hand they had in ATA's demise, but they're a big potential buyer for those...and ATA won't really have a say in who gets them.
