I'm betting a phone (if they do one) is based on the new nano look (the rounded sides, like the iPod mini) and not the previous-generation nano.
That would be more "grab-able" and comfortable to hold, I think.
If that recent rumor about Jobs talking this thing up to people is true, I guess it's a safe bet this thing exists and is on the way. Can't wait to see it. Hope it's something I can buy and use with my service (Cingular), if it's something that appeals to me.
EDIT:
quickie Illustrator CS2 3D mock... 
Rip off their existing stuff, sure!
I did the colors only because of Tuesday. Apple may just stick to black, white and silver? I do agree with others...probably has to be a slide off to expose a numeric keypad (IF the scroll wheel is there). Can't imagine dialing or entering info with keypad only, although that new search thing on the new iPods shows it can be done, I guess?)
Will be interesting, no matter what. I'd love to have a more modern, capable phone (camera, nice Apple software/way of doing things, a smidge of wireless capability, a little music storage, Apple style, etc.) than the one I have.