Apple has just been poor at projecting sales, and is caught low on stock. It happens, and it does not mean that 3G is imminent.
It may not mean that 3G is imminent, but I do believe that it points to the fact that a new device is coming sooner rather than later.
Also, to the people that believe that the existing device will continue to be sold after a new device is released - please explain your logic. Why would Apple let existing stock dwindle if they intended to continue to sell the device? They just prefer to take a little vacation from income?