There will always be something new just around the corner, so you cannot always "wait". That being said, I many times use this website to track updates, etc....I've seen too many folks go buy a new mac when it was widely known that the newer model was coming out like the next day....
http://buyersguide.macrumors.com/
Looks like the ipad3 will not be out for at least 3 months I'm guessing. I too have gone between the wifi version and the 3g version.....I have an iphone, so I believe I can tether if I need to but still have not really looked into it yet. I do not really want to pay for home internet, data plan for my iphone, AND a plan for an ipad....at some point it just seems redundant.
Right now because of the move I'm down to just having my macbookPro and my iphone4. I'll need another mac for the wife, just do not know what yet.
With the move a know there will soon be a buying spree in my near future....I need to buy another car or truck, a new mac, I want to upgrade my golf cart to a newer one, my wife wants a new vaccuum cleaner and new pots/pans, and I still need to build my new garage and lanai addition. I guess with a new address you buy new stuff.....
Sorry to go off topic.....
Frank