I have no idea how facetime would work on an iPod touch, but Steve did say they will ship tens of millions of facetime DEVICES this year (as other posters have mentioned), which I assume means that by the end of the year, other apple devices will get facetime. Unless Steve was lying or they plan on just shipping tens of millions of iPhone 4's by the end of the year which seems unlikely. I don't even think they could manufacture them that fast. My point is some other Apple device other than the iPhone will likely be getting facetime by the end of the year.
The only thing I really care about getting in the iPod touch is a still camera, I would prefer still over video, but if it had video then I would consider that a big bonus. Again, the requirement to get me to buy it is a camera. I do not have any sort of iPod yet, but I am very hesitant to buy it without a camera (regardless of what happens this september) because I just want a camera on the touch that badly.
The touch would sell like hotcakes if they did release one with a camera, I think pretty much everyone I know would upgrade, and probably hoards of other people, which would be tons of sales for Apple. Basically this would make every touch owner salivate with jealousy over it. Its pretty much a sure way to get touch owners to upgrade and to get more sales out of current touch owners that are satisfied with their devices.
I don't think this would even impact iPhone sales because I feel now like the iPhone is another whole segment of apple, as in if people want the iPhone they are gonna buy the iPhone and nothing else, they won't even look at the other products. People who want the iPhone 4 have already bought it or have plans to buy it very shortly, they do not care about waiting for September to see what is gonna happen with the touch.
I think the sales potential of a touch with a camera is absolutely huge, and way too huge for apple to ignore.
The stores here already seem to be emptying the iPod cases just like I saw last year around summertime, its clear that retail at least here will not be stocking any more of the current line other than current stock. The display units are gone from some stores already too with just empty holders in place now.