Digitimes is reporting that, according to an iPad supply chain source, Apple intends to ship 6 to 6.5 million iPads in the first quarter of 2011 (ending at the end of March). According to the source, 300,000 to 400,000 of those will be iPad 2s.
Digitimes' source also points out that Apple had about 1 to 1.5 million iPads in the inventory channel in January, and since Apple only ordered about 2 million iPads in January, it surmises that Apple is already planning to phase out the first generation iPad in favor of the iPad 2, of which we can assume production will be significantly increased in March.
However, if anything goes wrong with the production channel for the iPad 2, Digitimes points out that there could be a shortage of iPads because there will be no surplus stock of first generation iPads. Though, of course, this is speculation and, from Apple's track record, it is unlikely. Unless we're talking about a white iPad 2.