Your right if we are talking about Bigger Pixel site areas!A bigger sensor to archieve what? Same resulotion but better S/R and sensitiity or Higher resolution at same level of S/R and sensitivity? What does this tell us: 'we' hit the limits within the 36x24mm sensor size, 'we' cant no longer improve on one aspect without substantially sacrificing other aspects of the sensor?
I'm starting to repeat myself, but SNR is mostly dependent on sensor surface area. So a physically larger sensor would mean better SNR regardless of its resolution.
And if you can't reduce noise significantly (because technology is at its limits) the only thing you can do is enlarging the signal (equals to "more light" equals to "larger sensor").