I've seen apple screw people around too many times to be able to be confident that buying an iPad in June will equate to a good investment.
Then don't
I have seen what 4.0 adds, what the restrictions are and if anything the iPad is going to get better to use with 4.0. I know with open eyes than iPad 2 will be out next year and it will be better than the original.
However I bought a iPhone 1 and while some users held off said not till iPhone v2 or v3 (and used poorer phones while they waited) I had a good 14 months of using a phone that was way better (I thought) than anything else at the time. I did not care that a new phone would be out next year I just know I had a great device now.
If you are sure Apple are out to get you then just hold back and wait. Personally I will be getting a 3G one (when they ship) I know I don't NEED one, I know the next model will be better, but I also know if I get one I will most likely really like it and spend the next year (at least) using it.
The question is although next years model is always better, you have to decide when you buy one, I will might as well buy iPad 1 and have fun, if you want to wait for a better model that is cool too.
My point is no decision is wrong but everyones feelings on what is important when making a purchase are often very different. In my case I think having an iPad from day one and maybe missing out on iPad 2 for a while is better than waiting a year+ to even use one at all. I understand the logic behind the "wait and see" theory I just don't want to go that way.
Edwin