Time's up. If you haven't bought an iPad by now, don't. You've crossed the sucker line, and you'll feel like a grade-a chump when the next iPad comes out.
The basic rule of gadget-buying happiness is this: Don't buy anything after it's crossed the halfway point in its life-cycle. That's the sucker line.
When it comes to iPods and iPhones, the lifecycle is easy to grok: Apple produces new models like clockwork. Every September, new iPods emerge, tweaked this way or that way. And every June, there's a new iPhone. Apple hasn't produced multiple generations of iPads for us to pinpoint precisely when the next version will emerge, but since it uses mobile guts like the iPhone—and those mobile guts advance technologically at the same speed—it's reasonable to assume the iPad will see yearly updates just like the iPhone. Also, the steadily rising volume of tidbits about the next iPad indicate it's coming soon, lining up with a yearly update cycle.