Should I buy a new Apple Watch or just forget it?

AI has not been announced to the Apple Watches yet, following the announcement of Apple Intelligence. The Watches may not be powerful enough to handle AI yet. Though as your were saying the determining factor for you buying a new Apple Watch, you can stream music on your Apple Watch via cellular to Bluetooth speakers!

Play music on Apple Watch - Apple Support

If you were to buy a new Apple Watch, I would recommend you wait till September when they announce the new lineup. If you desire and you cannot wait, here’s the current lineup: Apple Watch - Compare Models - Apple

Good luck! 😉

That is a personal decision.

If you do not take advantage of any Apple Watch features, then I would say continue to use your Series 3 until it no longer updates, and then stop wearing the Apple Watch. Or maybe experiment and stop wearing your Apple Watch, then see if you find you miss any features. If not, they you have your answer.

I stopped wearing a watch about 30+ years ago, and at first I depended on knowing where all the clocks were in the office and at home. Then I got a Palm PDA and used that for time (among other things). That was replaced by an iPod touch, then the iPhone. But in 2018 I got a GPS Only Apple Watch Series 4. I have not stopped wearing it since, as I (and my Wife) enjoy it so much. Part of it is that I do not need to pull my iPhone out of my pocket for some of the more common things I can get from my Apple Watch.

Things I do with my GPS Only Series 4 Apple Watch: • It tells time, date, day of the week • Every iPhone alarm, appears on my wrist, where you can acknowledge it, dismiss it, etc… • I like the iPhone 3rd party “Alarmed” app (http://yoctoville.com), for my alarms • Ring.com door bell can display a static image on the Apple Watch • Weather (this gets used a lot) • MyRadar 3rd party app will display radar image • MyRadar and WeatherBug 3rd party apps will send you weather alerts • Make/Receive phone calls • Make/Receive FaceTime audio calls • Use Walkie-Talkie to other Apple Watches anywhere on the planet • Silence phone ringing by pressing the digital crown (great for SPAM calls) • Send & receive iMessages • Send & receive SMS TEXT • Say “Hey Siri, 14 and a half minute timer” • Say “Hey Siri, remind me when I get home to do xyz” • Say “Hey Siri, message my wife/husband/Susan/George/etc…” • Say “Hey Siri, start Outdoor Walk” • Say “Hey Siri, end workout” • Say "Hey Siri, find my iPhone" • Say "Hey Siri, flashlight" • Use a 3rd party garage door opener app and device (such as MyQ) • You can check your calendar • Read your email • If you need to take an iPhone picture where you cannot see the screen, use Apple Watch Camera app as a view finder/shutter release • 3rd party Ocean's Tide app for beach visits • Hand washing reminder and timer • Unlock your Mac (I do this several times a day) • Unlock your iPhone when you are wearing a mask • Track your exercise and physical activities Since my Wife got her Apple Watch, we have been able to reliably iMessage each other, as she never keeps here iPhone on her person. If my Apple Watch was lost, stolen, or broken, I would order a replacement as fast as possible, as I would miss it so much.

Why cant you use bluetooth speakers with your current watch? You should be able to download music and use it that way. No need for streaming

While you’re wearing Apple Watch, your Mac can sense when you’re nearby and automatically log you in. If you have a Mac (mid-2013 or later) with macOS 10.13 or later, your Apple Watch can instantly unlock your Mac when it wakes from sleep. Here’s how you can set it up: Unlock your Mac with your Apple Watch - Apple Support

I have been unlocking my Macs since I got my Apple Watch Series 4 GPS Only in 2018. I would NOT get a Series 4 today, just because it is most likely going to drop off the edge of new update support, but if you already have one, it works very well to unlock your Mac.

I unlock my work Mac several times during the day using my Apple Watch. I also unlock my personal Mac. Maybe once or twice a week, I might have to actually enter my Mac password, but the rest of the time, the Apple Watch unlocks my Macs. My Macs are running Sonoma (latest update as of noon today), and Ventura (last year's, but with the most recent update). So, "No", cellular is not needed to unlock your Mac.

As to which Mac it unlocks. You press a key on the Mac, and the Mac reaches out to the Apple Watch for approval to unlock. So it is the Mac you are using that gets unlocked. Unless you touch the Mac, it is not going to unlock. You can walk past your Mac all day long and it will remain locked until you press a key on the keyboard.

As to the oldest Apple Watch that supports new features, some of that depends on Apple Watch hardware. My Series 4 is on watchOS 10.6 (latest), but there are some features my hardware does not support. But all the strictly software features are working on my Series 4. Again, I would not get a Series 4 today, only because it will stop getting new updates real-soon-now.

Almost nothing in the Apple Watch "Requires" cellular. If your iPhone is nearby, the Apple Watch will ALWAYS ask the iPhone radios to make the connection, and the Apple Watch will use low energy Bluetooth to get the information from the iPhone. Even if it is a cellular model. The cellular radio just gets used when the iPhone is not nearby and there is no WiFi available, then the Apple Watch will connect to the Internet via the more power hungry cellular radio.

If you always have your iPhone nearby, then it will do EVERYTHING the cellular model will do, just using the iPhone's radios.

NOTE: Occasionally, when I go to wake up my Mac, it will want a password (or fingerprint). I can sometimes press the "Escape" a few times until the screen blanks, then press a key on the keyboard again, this time the Apple Watch will unlock it.

I suspect that any Apple Intelligence on the Apple Watch will be provided by the iPhone, for many years to come.