The iPad 1 section is still going even. Some slow down on this one, sure, maybe a little, but I am sure it will still be rolling, not to mention the general discussion that applies to all.
I think a lot more 2 owners may hold out. Sure the retina display and faster processor, better camera are quite nice, but for me, I don't use the camera on my iPad 2 anyway, the processor is excellent, and I quite like the display just fine. I also think the iPad 1 is still quite fast enough too, and continue to use that to surf every few days. Until 3 weeks ago, I was merrily rolling along with my 1. I just got the 2, so I'm not going anywhere.