It is entirely possible that the shipping estimates have slipped because many customers have decided to opt for the larger iPhone 6 Plus rather than the 4.7-inch iPhone 6. It could be that the Full HD resolution and optical image stabilization are reason enough to go for the larger and more expensive model.
Alternatively it could be that the rumors were semi-accurate and that supply is constrained, albeit enough for Apple to announce it and sell at least some units. It is possible that you could still find units for pre-order via third-party retailers and carrier websites, or the next best thing we guess is to wait for launch day itself in which you might be able to pick one up for yourself by heading to an Apple store.
Given that we have heard how Apple is now handling physical pickups by giving them digital reservation passes, it means that you won’t have to stand in line for hours to get one, but should be able to get a digital reservation pass and pick it up later in the day.