The Watch is either half empty or half full. ;-)
There are always dreamed-for new features, but not everyone dreams of the same new features. This site has a section devoted to the current models and the rumored features-to-come -
https://buyersguide.macrumors.com/#other If you think the rumored new features are worth waiting for, then wait. If they don't excite you, why not get started now? The basic fitness capabilities of even the first-generation Watch (and Apple's approach to that functionality) have helped me greatly improve my overall fitness. Essentially, any Apple Watch is better than none.
I've had the first-generation Watch and currently have a Series 4. The Series 4 was a great jump in performance and usability over the first generation and though there have been new features added with the Series 5 and Series 6, none of those features are so compelling that I'm ready to retire my Series 4. Other people feel differently.
Fortunately, my health is such that there are no biometrics that are a "must have." To me, heart rate is necessary for measuring the intensity of workouts rather than warning me of danger. I've used the ECG a few times as a matter of curiosity. Blood pressure monitoring would be a nice addition, but again, not essential to my health maintenance. But each of us has differing needs in that regard. I can't say to you, "You should wait for...", only you know your health needs.
Overall, I don't see any major shortcomings - it's not the way my mind works. "If you can't be with the one you love, love the one you're with." Battery life for me is excellent - I wear my Watch from the moment I wake until I go to sleep, and it never needs to be charged in between. However, I don't have a cellular data plan for it and even if I did, I make few phone calls, receive relatively few text messages, don't get a whole lot of push notifications, am rarely away from Wi-Fi (mostly during my daily one-hour walks), and don't stream music to/from the Watch. So I also don't put a lot of load on that battery. I haven't wished I had an always-on display, the size of the Series 4 display was a big improvement over the first-generation display and I've yet to wish that it was even larger. Overall, I'm likely to keep my current Watch until I need to replace the battery or if I damage the display. So maybe I'll be getting a Series 7, or maybe even Series 8... the one thing that's certain is that Apple Watch has become a permanent part of my lifestyle.
