That's a tough one - it's already "obsolete" from a computer-hardware perspective, as Apple no longer offers software updates for it; and I'm sure eventually it won't connect to "then-current" iPhones any more, which would make it near-useless other than to display the time.
As a "fashion timepiece" it kind of fails, too, since it's usability will be shot. One thing about high-end watches, they don't stop working just because computer technology has increased.
Then there's the battery. Eventually the battery won't hold a good charge, and it's possible/probable that no good replacements will be available. A big example of this is the "Pebble Time Round" smartwatch. It used a custom battery, and after the Pebble company went under, no replacement batteries are available. So Pebble Time Rounds are starting to fail (hold less than a few hours of battery life,) which makes them effectively useless. (And their software still connects to modern phones.)
So, that leaves only two major "collectible" points - raw gold value, and "important Apple artifact." In raw gold value, it's probably worth far less than the original cost. In "important Apple artifact," I expect it will end up collectible. Although I don't know if it will ever be worth more than its original high sales price. It was almost certainly a very low-production-volume product, and "unusual, expensive, low-production-volume" Apple products tend to become collectible, even if they are somewhat limited in their usefulness. (See Twentieth Anniversary Macintosh.)