Minor hardware revisions are common in electronics. As parts get smaller, cheaper, and draw smaller amounts of energy, companies swap out the internals for identically-functioning new versions. It's no surprise that Nintendo is looking into alternate accelerometer chips to provide the motion sensing functions of the Wii Remote, or that companies who manufacture accelerometers are clamoring to get their devices into the controller, thus ensuring a constant demand for their chips. Nintendo is currently looking at samples sent from many different manufacturers.
According to a Nikkei Tech-On! article, one of the companies, Kionix, may make it possible to increase the sensitivity of the accelerometer's motion-sensing. Nintendo has yet to make any decisions. "It is difficult for manufacturers to be selected as a new supplier," an employee of a sensor company told Nikkei.