iPad 4 owner here. I don't plan to upgrade. If I was loaded, then yeah, I'd upgrade every year and not even think about it, but there isn't enough new here to warrant me spending the cash to replace a perfectly great-working iPad. I also am not a constant iPad-user. I do most things on my phone or laptop so I'm really more of a casual netflix-in-bed iPad user.
The most compelling things to me are the thin factor (the iPad 4 is a heavy beast by comparison so that would be nice), the lower reflectiveness, and maybe the faster processing. But it's still running the same resolution, which is now a much lower dpi than the new iPhones, so I'm not compelled to replace my ipad when the new one basically has the same quality display.
What I'm waiting for- to find out about this "ipad Pro". Since next year I expect to get the iPhone 6 Plus S, I will find less of a difference between ipad and iphone than there currently is for me and I might find a bigger iPad more interesting.
Pie in the sky- I've heard random rumors about future versions of ipads with sophisticated haptic texture-simulation and also Apple's been snapping up patents of 3D and even holographic displays. I know that's a ways off, but until then an iPad is just an iPad and a couple generations still isn't enough of an upgrade to justify the expenditure for me.