This was not a rumor this time. The iPod nano 4th generation player images were leaked and were the real images. The one who took the photo was sure that it was the “verified authentic photo” of the new coming iPod nano.

Its tall and thin and nearly looks like Zune, if the ends are not curved and mid part is not bulged. This was taken when the iPod packaging was being done so here is one of the pics with the 4th generation iPod in the case.
And it is expected that 9th is the date for the release of these iPods, as said by Engadget -

Looks like that Apple event for the Tuesday, the 9th of this month is on. We know it’ll be new iPods (they always do iPods for the fall / holidays), but hopefully they’ll have a little something special for us. Whatever, just as long as it’s not that round, awful looking nano. Go on, hit the comments and get speculating.