Yes! According to the sometimes accurate and always wittily sarcastic (in a British sort of way) Register.co.uk. They go on to give all of the prequisite "rampant speculation alerts" but say they have contacts inside mobile operators (ahem O2? you are now on Jobso's shitelist) who have seen the device.
According to their source, the slide out keyboard isn't perfect but it does work and there are prototypes aimed at the corporate market. That would indicate that they will be available fairly soon. El Reg says one year, but that seems kind of a long way off if the carriers are already messing with it.
(Yeah we know that isn't an iPhone to the right but an iPhone with a slider would most likely look like this.)
