The problem comes if you keep the sensor size fixed; does the extra resolution you get from more megapixels outweigh the decrease in signal-to-noise ratio (assuming comparable technology; this years 8MP sensor way well have a better signal-to-noise ratio than last years 6MP). There has to be a point beyond which extra resolution isn't important.
----------Thanks, John. You have nailed the question we should all be asking when the *ist D's successor comes in at 8 mp in APS-C.
Joe
