How can the airlines be surprised that the premium traffic is going to business jets? The airlines have eroded the quality of service in the premium cabins down to what coach used to be a few years ago. The people that want the service and don't so much care about the price are going to find an alternative.
And then there is the TSA hassle, which applies equally to all airline passengers, premium or coach. Compare the TSA hassle and advance boarding requirements to the zero hassle and zero delays at the FBO, and you can see why private aircraft makes a lot of sense.
I do believe the title of the thread. Just like in Europe, where intra-Europe business class is just a glorified coach section, I believe that the same will happen in the U.S. First class seats will be eliminated. Netjets and DayJet and other such operators will ultimately syphon off all the premium paying passengers.