All of the 757s have winglets. About half of the 763s have winglets. More importantly, they just committed to redoing the whole 75/76 fleet with Flat Panel displays, about half of the fleet is done. So they aren't going anywhere anytime soon.

The 737s will replace most of the S80s... but I believe AMR wants to diversify its fleets a little more in case the whole Boeing line ever gets shut down for some reason. I think the Airbii will replace some of the S80 fleet as well as some domestic 757s (eventually.)