Even at a fixed print size, I want to use the biggest sensor that is practical (and affordable) enough. While APS-C is good and will only get better, the same really applies to Four Thirds and even smaller sensor sizes.
How will these sensors get better?
Will the quantum efficiency double? (no, QE is already high)
Will they cram more sensor sites on the chip? (probably, the D800 performs well)
Will they use fundamentally different technologies? (this is already going on with Foveon and XTrans, but so far innovation has not appeared in m 4/3)
This is not to say revolutionary sensor technology will never happen, of course it will. However sensor technology change proceeds slowly.
The real opportunity lies in lens development.
When perspective remains constant, an increase in lens surface area compensates for the signal-to-noise ratio and dynamic range handicaps associated with smaller sensor surface areas. You don't need to wait for Adobe (or anyone else) to figure out how to demosaic a new sensor technology if you can provide super fast, optically excellent lenses for Bayer sensors with thoughtfully designed AA filters.
Fast lenses only provide more signal in the signal-to-noise ratio equation. They do not deliver more pixels. People whose work relies on very large prints (~48" or more) of detailed subjects won't be interested in APS-C or smaller formats. This sort of work is expensive as it demands large sensor surface areas, excellent optics and a sturdy tripod.