You'd assume the battery will have a limited lifespan at least, yes.
If they are smart, Apple will sell the most expensive models with a 'lifetime warranty' - basically you keep the frame that's made of precious metal and every so often you can have the internals upgraded to the current model for a relatively reasonable price - say twice the price of the base model. However I suspect the Apple Watch Gold will be purely for people who literally have more money than they know what to do with; people for whom the idea of spending another £6K in a few years doesn't actually worry them all that much.