There is a general consensus that iPad 2 will come out near the end of March or perhaps the first week of April.
Occasionally a rumor will pop up about an earlier release, but the most recent info about manufacturer ramp ups suggests March.
Of course Apple hasn't made any statements - and the iPad has just been released within the last couple of months in some countries.
The guides on Mac Rumors are generally for well established products that have had 3, 4, or even more releases. That helps establish a pattern of updates to make predictions from. There is only one data point for iPad, so folks have been basing their guesses based on the iPhone release cycle.