We know that Kindle is now Amazon’s most popular selling item, but the company is still vague about the details. Today, AppleInsider is reporting that Analyst Ming-Chi Kuo of Concord Equity Research, estimates that Amazon has sold 5.4 million units this year and Kuo expects Kindle shipments to reach 4.5 million units in the first quarter of 2011.

According to Kuo’s latest report, the iPad is keeping up with the Kindle. AppleInsider has more: “Shipments of Amazon’s Kindle from suppliers in Taiwan reached 1.6 million units in December, matching the month’s estimated iPad production, although Apple is ramping down to accommodate the coming new version, a new report says. Apple has shifted iPad production from an estimated 2.1 million units in November to just 1.6 million in December in order to prepare for the launch of revised new tablet, expected to be announced in January.”

Do you think 2011 will be the year that tablets and eReaders become mainstream?