A good watch can last a lifetime and don't really date, in fact if you buy the right one they can appreciate in value
Can you honestly see yourself wearing a first generation Apple Watch in 10 years time!
Nope, of course not, but straps will be moveable across generations (I'd hope). I upgrade my hardware often, it's one of the things I purchase often, so knowing me I'll end up getting the newest generation Apple Watches too.
Who knows how things will be in 10 years time, but ultimately I am getting the use out of it now, which I am happy with, which is the point of me buying it.