One of the surest signs of an Apple product being replaced/refreshed is that said product is no longer available and lacks an expected availability date. The latest product to go unavailable w/no expected availability date is the iPhone.
"The change follows multiple weeks during which the American website had already cited delays of between five to seven days for new orders.
Apple's shortfall for its direct channel is also the culmination of a slowly widening shortage that first became evident in late March, when stores in New York City began having trouble carrying the devices -- a supply problem which eventually spread to all US retail and has only been partly resolved in the near term."
The long rumored 3G iPhone could very well be announced at any time.