No one expects that, not even Apple. At least not in the first year. Mobile phones (in general) are one of the hottest and highest number, in unit sales, electronic products on the planet. If not THE highest.

I expect a few million by the end of the year. Some analysts are predicting 4 million+. I don't know if I'd go that high at the moment, but it very well could when we see the new landscape of the app store in March and May. I really don't know how many Apple is targeting and unless they make a public announcement, I don't think anyone will ever know or have even a remote chance of guessing (reasonably).

I do think that if 3 or 4 million units were sold, Apple would likely be "satisfied" if not outright happy. This isn't the AppleTV. They seem to actually be putting some effort behind this one. In the past week I've seen people mention three Apple failures: Mac mini (hardly), AppleTV (probably still sells more units than any other media streamer) and the HiFi speaker dock for the iPod (why bother even bringing this one up?)