Burt Rutan had comments about this at last year's EAA Convention.
He recommended that the next step be an electric plane with a special purpose design for doing aerobatics in air shows.
A standard act is only about 15 minutes, which is within the current practical power design restrictions.
Burt stated that propeller drives didn't need to be only put on the front or back of the plane inline with the forward motion. Smaller propellers with motors could be put on the wing tips and/or tail to create unique aerobatics.
Back to my point of view:
Throughout aviation history, it's the engine that drives aircraft innovation:
The Wright Flyer wouldn't have existed without Charles Taylor's lightweight engine.
The P&W R-2800 Double Wasp enabled many aircraft designs from the B-26, P-47 and Douglas DC-6
The P-51 wasn't the success without the Merlin engine.
The 747 couldn't have existed without the high-bypass turbofan.
The 777 wouldn't exist without the huge power engines.
The 787 and any future airliner design wouldn't exist without an engine with better fuel economy.