I spent some time speaking to a Premium Reseller in Hong Kong about the iPhone 3G today. Since the beginning of February Apple Resellers in Hong Kong are allow to sell the iPhone 3G without a carrier contract, and most importantly, like all legitimate iPhone 3G sold in HK, also officially unlocked by Apple. Most of them are selling the models (8GB an 16GB) of the iPhone 3G at Apple HK's SRP of HKD5400.00 and HKD6200.00 respectively.
Although because of the profit margins Apple is offering it's resellers, some resellers have insisted on adding a 3rd party case with each iPhone 3G sold, to enable then to sell the iPhone for an additional HKD100.00.
The reseller I spoke to also believes a new iPhone will be released in June, but like other product launches in the past, the new iPhone probably will not be available in HK, in large quantities, until August or September.
This means if you buy an iPhone today, you will have used the iPhone for 6 - 7 months by the time the new iPhone arrives.
The new iPhone will likely be a model with more features and better specs than the currently available iPhone 3G. Rather than a less featured model relative to the current iPhone 3G.
Apple's normal practice is to stick to the pricing ranges of past models and have the new and better model takes the top end of the price range.
Therefore if you need or want to get an iPhone. You should either purchase a used iPhone (1st generation) or one of the iPhone 3G (8GB) today. So you will have used your iPhone as long as possible before the new version comes out.
For most users, the new, more advanced iPhone, may not be something the average users need or have to upgrade to; at least not for another 12 month after it is available.