Everyone here is bashing these rumors as if apple.pro is claiming this product is due to come out. Not the case!
I think very many people here need a better understanding of the R&D phases technology companies such as Apple go through. There are probably several dozen iPhone prototypes of various hardware configurations and form-factors. This is not to say that any of them will come close to seeing the light of day.
Personally, I think Apple would be stupid to release an iPhone with a slideout keyboard, just as others have said. However, I also think they would be stupid to not have any sort of keyboard in development just in case. Remember, when the iPhone first came out in 2007, it was one of the only smartphones without a keyboard and it's main competition was RIM. For a company as large as Apple who has significant future revenue riding on the iPhone product line, they need to develop several models simultaneously just in case. It was uncertain whether enterprise would adopt a smartphone without a keyboard - it would prudent to at least have a prototype model.
Remember when Apple revealed they had been secretly developing a parallel version of OS X built to run on Intel? No doubt the same sort of things are going on in the iPhone division.