https://www.cnet.com/news/watchos-5-comes-to-all-apple-watches-september-17/

Even if you don't get the Apple Watch Series 4, your current Apple Watch will still feel new.

That's because Apple is releasing its latest Apple Watch software update, WatchOS 5, on Sept. 17. Apple revealed the launch date for WatchOS 5 at its event on Sept. 12.