Users of older Apple Watches will want to upgrade to a new Apple Watch with the release of watchOS 6

Zac Hall for 9to5Mac.:

watchOS 6 includes six new watch faces with even more customization options for personalizing your Apple Watch — if you have a Series 4 model. The upcoming software update is also coming to Apple Watch Series 1 through 3, but you’ll need to upgrade your Apple Watch if you want to try out all the new watch faces.
Older Apple Watch models will be limited to two new watch faces: Numerals Mono and Numerals Duo. Both are cool watch faces with options for changing color, typeface, and style, but neither support showing any information beyond the time.
If watch faces aren’t a priority for you, Apple Watch Series 4 offers a number of other improvements too: faster performance, new case sizes with larger screens and smaller bezels, louder speakers, haptic feedback from the Digital Crown, a built-in ECG app for capturing an electrocardiogram, and fall detection with the ability to notify emergency services and share your location with a contact if you’re unresponsive.

MacDailyNews Take: If you havent upgradeed from Series 3 or older, don’t bother with Series 4 now. It’s only 3 months or so until Apple Watch Series 5 is expected to debut!