First, it should be noted that Ralph de la Vega, AT&T's Mobility CEO, says his company is expecting to have all smartphones in the network integrated with 3G in a matter of months, which makes me think the iPhone 2.0 update may bring 3G to older models, although that is widely known as impossible, for now. Well, I guess we should live and see, shouldn't we?
Now, considering that Shane Wu from American Technology Research already said the 3G iPhone will arrive in June-July, this is it! Anyway, if it is possible, I am sure Apple will bring a software update to unleash 3G capabilities on older iPhones too, but this is also something that only time will tell.
In the meantime, if you consider buying a smartphone and can't really decide about what to buy, feel free to check some iPhone reviews. It may not be the "smartest" phoine around, but it surely has "the WOW! factor..."