I bet we'll see more turbines in the future of GA and EAA'ers but I believe they will be in purpose built airframes, probably resembling Long EZ or wing and boom type shapes with the jet exhaust in the rear.
The 'next generation' very light turbofans will have much better efficiencies. However, my best guess is that turbofans will always be pricey due to the exotic materials and engineering tolerances required, to spite the fact that they are simpler in 'theory' than a piston engine.
Agreed, turbofans will also always perform most efficiently up higher in thin air where fuel burn is relatively low and airframe drag is equally low for relatively high true airspeeds. I would not be suprised to see efficiently low fuel burns for optimim economy cruise flight profiles for tomorrows turbofan GA planes that approach the more inefficient 100LL burners of yesterday.
But... Jets are lousy at pattern work if you are paying the bills, and equally wonderful at pattern work if you are not paying the bills and just flying them
It's still a ways out though. I'd 'settle' for a nice RV for now
