This will never happen. The R & D of such a project would cost billions. With Boeing and Airbus producing the A380, A350, and B787, we won't see anything in this arena for the next 20-25 years. At least not flying the line. You may see designs, but nothing built and flying for airlines. I see a replacement of the B737/A320 happening in 10 years. I remember in the early 90's as a teenager seeing design images of the A3XX "Double-Decker" airbus. Finally, 15 years later, it was in service.