iPhone Nano is coming soon according the latest rumors; MacWorld is coming soon in a few weeks, there is rumors that Apple will introduce a new iPhone Nano on the event.
Someone also uploaded a picture of the iPhone Nano next iPhone 3G.
One of the iPhone case manufacturer already selling iPhone Nano case on their website. (iPhone Nano Case) This is the same manufacter who sold iPhone 3G case before the iPhone 3G being announced.
However, there is also rumor that Steve Jobs would not making the keynote on MacWorld which is something he used to do on MacWorld events.