Except that a smartwatch is no more a watch than a smartphone is merely a phone... A watch tells time and a phone lets you call people. Yet, calling people is a fringe use case with the iPhone and all the other smartphones. Likewise, telling time will be a fringe use case with the Apple Watch.
I haven't used a watch for more than 20 years. Simply because having the time on my wrist is pointless, I have plenty other ways to tell time without burdening my wrist with a chunk of metal. But I will buy an Apple Watch, because I can see many use cases for having a computer on my wrist.
Moreover, the Apple Watch will be bought by individuals, not business. The concept of "losing value" is pointless for individuals. They're not in the business of reselling used watches. They're in the business of using them. For an end-user, an items loses its value when it's either broken or cease to allow them to perform useful tasks with it. The watch will not stop working after a year. It will not stop performing tasks either. So it will be still have its full value.