If you wait for the newest and latest technology to get better and cheaper before buying, well, then you'll wait forever. All techno gadgets get better, cheaper, or both, over time. And lately, "over time" means just a few months.
Sometimes you just gotta decide how bad you want something, man up, and go for it.
That said... I've been very successful in selling my older technology as I upgrade to new. When I sold my iPhone 3G last year, I sold it for MORE than it cost me to upgrade the iPhone 3GS (not counting AT&T service, which I would have been paying for anyway). So moving to the iPhone 3GS was a no brainer. More recently, I sold my original iPhone (which had been sitting in a drawer for 18 months) for $200. Lost money on that one. I should have sold it when I got the 3G. But I was expecting my wife to use it.
I've got the 3G iPad w/64GB on order. $829. In a year or so, when the 2nd generation iPad comes along, I'm betting I'll be able to sell my 1st one for at least $500-$600. Sure, it depends on how the 2nd generation models are priced, but I think the 2nd gen models will end up adding more features for the same price... something Apple likes to do a lot. So, assuming I can get $550, that means my "rental" of the 1st iPad for a year was less than $300. About $25 a month. Not a big deal.
Do you really want the iPad now? If the answer is yes, go for it and worry about the future when it gets here!
Mark