I am going to have to disagree with you on Apple selling a nano and a mini because they are too close to differentiate. Without the hard drive the mini can be just as small as the nano so what would Apple do with the extra "wasted" space? I think the nano will get video support while keeping the click-wheel, the size of the nano will stay the same, but the screen will get bigger so you will have to turn the nano sideways to watch video.
the current nano need to compete with all the other MP3 players that are cheaper smaller but includes a screen...
The new mini will keep the form factor of the 5.5 gen iPod because lots of people would like to have bigger screen than the current nanos without having to buy the top of the line ipods....
people don't buy ipod based on the internal components but with external form factors and functionnalities... the new nano is the new mini...