A number of well-placed and well-respected journalists that have covered Apple for many years and have got contacts within the company have written that Apple will not be releasing the iPhone 5 at the forthcoming WWDC in San Francisco in June.
A few reasons have been put forward to explain why this might be the case; the Earthquake in Japan followed by the nuclear accident and the human tragedy and disruption that followed could be part of the problem. We've heard that another big handset manufacturer may be running into serious issues with sourcing components for its smartphones from Japan as well.
Then, the iPad 2; the device's success means that more of these will have to be produced as soon as possible, putting a huge strain on supply. Most of the components in the iPad 2 will be used in the iPhone 5 which means that if component supply is very constrained, Apple may decide to prioritise production of one device over another.
Then there's the Verizon customers; Macobserver reckons that Apple and Verizon might have an agreement to delay the new iPhone 5 to avoid any backlash from their existing customers who may be angered by the fact that their handsets is obsolete within six months.
Finally, there are signs that iOS 5 will integrate cloud-based services and it is very likely that integrating these features into the new OS is taking more time and resource than expected, especially since many big projects (like the construction of a data center) will need to be synchronised in order to succeed.
In truth though, it is likely that any delay in the launch of the iPhone 5, would have come following a combination of reasons, none of which Apple will ever disclose.