To get a general idea of how many Nook Colors will be sold this holiday season, you can look to some quotes from Barnes & Noble Chairman Len Riggio in a recent Publisher's Weekly article naming Riggio PW's Person of the Year.
Riggio says, "B&N is manufacturing Nook Colors at a rate of 18,000 per day and is loading up a 747 every four to five days to bring devices to the U.S. from China." He adds that, "We'll be up against it to produce enough for the [holiday] season."
PW also quotes Riggio saying that he "expects demand for all e-reading devices to accelerate in 2011 because of positive word-of-mouth from customers, before tapering off in 2012." He then talks about how prices will continue to decrease for e-readers as more functionality is added, but he doesn't explain exactly why he thinks sales will plateau in 2012.
Neither e-reader leader Amazon nor Barnes & Noble release specific sales numbers for their devices (in October, Barnes & Noble said that it had sold more than a million units of the original Nook). But if you do the math based on Riggio's numbers, Barnes & Noble would be in line to sell well over 500,000 Nook Colors this holiday season. According to Reuters, Forrester Research estimates that Barnes & Noble will have sold 2 million Nook devices by the end of 2010, "closing in on Sony's Reader for second place" in the e-reader market.