The release is expected to take place sometime around June during the Apple's developer's conference and the next iPhone will be featuring with a 4-inch screen. The fifth generations of iPhones will most likely feature 4-inch screens, by doing so Apple plans to compete with the Android based smartphones that have screens ranging from 4-inches to 7-inches.
There are also rumors abound that this time Apple would be coming out with a smaller and cheaper iPhone. All these mark a shift in the Apple's strategy of releasing only one iPhone at a time. As Android based smartphones gain popularity Apple is being forced to re-think its strategy to retain its market share.
Another set of rumors indicate that Apple would be coming out with iPhones in various screen sizes and also iPhone 5 would most likely be having a concealed keyboard.
The next iPhone release will happen around June, until then we will have to wait and see whether Apple comes out with a 4-inch screen model or iPhones in various price bands and sizes. We will find out whether the rumors regarding iPhones are just rumors or there is some truth in them.