Last month, well ahead of the iPad 2's launch, Daring Fireball postulated that Apple might release the iPad 3 this year as well. The reasoning behind it was rather solid. April is too early in the year for a major launch. It may have a chilling effect on purchases made over the holidays. In essence, Apple wants to avoid people holding off on buying iPads until the summer.
September seems like a more reasonable month to make their yearly update to the product line. Unfortunately, since the market was moving forward so quickly, Apple couldn't afford to wait eighteen months for an iPad follow-up. So we get an iPad 2 launch in March, and an iPad 3 launch somewhere around September.
Two iPads this year, one iPad every September in subsequent years. And there are logical options for how the iPad 3 could build on the iPad 2 without negating it. For instance, Apple could make the iPad 3 an LTE version of the 2. Or the iPad 3D could launch.
Apple is perfectly capable of launching a new iPad in September, without it being the iPad 3. An LTE iPad 2 would be deserving of its own September event, and that could be enough to 'reset' the iPad's regular refresh date. There are other options too- any iterative improvement would do, if Apple's goal is moving the 'iPad event' to September.
No matter how they do it, if Apple changes the iPad launch month to September, early 2012 is going to be very awkward. We aren't likely to see an 'official' Apple announcement ever on just when the iPad refresh month is. Competing tablet makers will be left with two choices.
1. Either roll out your products in Q1 and suck as much of the limelight down as you can, while you can.
2. Roll everything out in Q3, right alongside the iPad, and trust the glut of Christmas dollars to sustain you.
Neither is ideal. But Apple isn't in the habit of leaving anything but scraps for their competitors.