Remember: A lens is not guaranteed to perform in a 5-Mpixel camera simply because it is specified as a 5-Mpixel lens.

Edmund Optics and Schneider Optics explain aspects of matching one technology's advances with another's.

Pictures and arrows at the following link:

Matching Lenses and Sensors

Greg Hollows and Stuart Singer—Mar 1, 2009

Each year, sensor manufacturers fabricate sensors with smaller pixel sizes. About 15 years ago, it was common to find sensors with pixels as small as 13 µm. It is now common to find sensors with standard 5-µm pixel sizes. Recently, sensor manufacturers have produced pixel sizes of 1.4 µm without considering lens performance limits. It is also common to find sensors that contain 5 Mpixels and individual pixel sizes of 3.45 µm. In the next generation of image sensors, some manufacturers expect to produce devices with pixel sizes as small as 1.75 µm.