IMHO, you are not seeing in its best light. The Apple Watch is, by what we saw, a watch with really cool other features - and those features will keep running as long as the watch does. But it is mostly a watch.
In this sense, it is just a regular watch you purchase today: it is only a watch, with the functions that was designed by in its creation process. Usually, next year collection of watches changes the form, add or adjust some functionalities, colors, whatever, and your watch is still your watch and you will still be able to do the same with it that it was designed to do.
Apple Watch 2 will or 3 or 4 will not render your watch obsolete, it will probably have newer and/or advanced capabilities that yours do not, but the core use that is serve as a watch, and a smart one with a calendar, payments, notification, everything, will keep rolling indefinitely.
Like the iPhone 1, it is still usable as a phone, to send and receive text messages, to navigate the internet, to send and receive emails
not as fast, with not as much advancements as a iPhone 6, but It is still and iPhone nevertheless.
Moreover, any traditional watch, by definition, are already obsolete as this newer ones also serve to register time and many other things...