Aps Cameras How Many Megapixels An APS-C Sensor Can Take Before Noise Start To Be More Obvious?

How many megapixels an APS-C sensor can take before noise start to be more obvious? - aps cameras

With all the DSLR manufacturers race against time CRAM more megapixels, its APS-C, I wonder who will come a time when digital SLR cameras more compact with the noise? And what is the ideal MP APS-C?