If they have seen something Apple didn't want them to (or has forbidden them to disclose), it could be a prototype or early sample of the product, or it might just be one of several candidates.
Or it could be misinformation from Apple, or just a complete fabrication.
Anyway, iLounge is tipping that the next model iPhone will have a similar industrial design to the iPhone 4 and 4S, but slimmer and taller, with a partly metal back panel.
The extra height is said to be needed to accommodate a 4in (rather than 3.5in) screen with a different aspect ratio. Some iPhone owners do seem to be feeling some screen-size envy with regard to several recent Android phones, but the idea of yet another variation in pixel dimensions among iOS devices is questionable.
That said, iLounge readers have come up with some suggestions for how the extra real estate could be used without requiring developers to rewrite everything. These include a permanent row of icons/buttons (a la the Mac OS X Dock), support for the extra rows of pixels being delivered via CocoaTouch so apps that don't use bitmaps can automatically expand, and simple letterboxing/pillarboxing (depending on orientation) for those apps - notably games - that have hard-coded dimensions.
Page 2: new Dock connector?