What made the iPhone so futuristic was it's touchscreen-only user interface. Adding a keyboard might just ruin it all. However, adding it with style, such as on the TYTN II or the XPERIA X1 might attract business consumers.

Besides a front-facing camera and a better back camera, the iPhone actually needs a hardware keyboard. For some functions a touchscreen keyboard is nice, but for others you would actually like to have a hardware keyboard. Look at the Nokia N810 Internet Tablet: it has a slide-out keyboard, and still looks great. Here's a quote from our source:

What he is apparently doing is canvassing the idea with operators. “If you had a keyboard version, how many would you take?” And he has taken this beyond just chatting: actual prototypes - not just mockups - have been sent to senior executives at some operators. I’m not allowed to even hint which operators… but I can report that the keyboard has “issues” which are not yet resolved.

Source: The iPhone Blog