Everyone is expecting, like in the past iPhone release dates, that it will be sometime near the end of the summer, a few weeks before the iPod touch 4g
There also are rumors that the iPhone will move over to Sprint for some crazy reason, i personally have no idea as to why they didnt pick Verizon instead.
But, as usual, it willreplace the price of the current iPhone, because usually the iPhone keeps the same price, but then the older models, their prices drop dramatically
So you could run to your local at&t store and ask them what the price is for an iPhone, and i can almost guarantee that it will be the same price when the new one comes out.