On Fox News today the FAA announced that they are going to go ahead with upgrading our ATC from radar based systems to GPS systems which are much more precise, and therefore they can pack the air traffic a lot closer. An FAA spokesman said that right now we have the best ATC system in the world, however it is stretched to capacity and then some. The new GPS ATC system will allow us to handle a lot more traffic. If I heard right it will be in place in around five or more years.
Here is an article touching on this from earlier this month:
PS: Almost forgot. Since this system will also require digital communication between planes in flight, it sounds like that means we'll all have to upgrade our instruments with this new GPS based ATC hardware in our various aircraft, be it 777, Bonanza, or what I'm flying right now, paper airplane! :)