I read an article a couple months ago stating that Delta is looking to retire their fleet of 747's. I think they are going to be replaced by 777's.
While the 777 is a nice looking aircraft, I think the 747 is a nicer looking place. But when you consider it's been in service for over 40 years, it is a bit long in the tooth. I'm actually kind of surprised that Delta isn't going to get some of the 747-8 models but I guess the 777 uses less fuel.